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| committer | Roger Frank <rfrank@pglaf.org> | 2025-10-14 20:00:30 -0700 |
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diff --git a/33925-h/33925-h.htm b/33925-h/33925-h.htm new file mode 100644 index 0000000..66747fb --- /dev/null +++ b/33925-h/33925-h.htm @@ -0,0 +1,5429 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> +<html> +<head> + <meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1"> + <meta http-equiv="Content-Style-Type" content="text/css" > + <title> + The Project Gutenberg eBook of The Geological Story of the Isle Of Wight, by Rev. J. Cecil Hughes, B.A. + </title> + <style type="text/css"> + + body {margin-left: 10%; margin-right: 10%;} + p {text-indent: 2em; text-align: justify;} + hr {width: 95%; color: #000; text-align: center;} + table {margin-left: auto; margin-right: auto;} + .pagenum {position: absolute; text-indent: 0; left: 92%; font-size: .86em; color: #808080;} + .smcap {font-variant: small-caps;} + .vtop {vertical-align: top;} + .vbot {vertical-align: bottom} + .center {text-align: center;} + .text_lf {text-align: left;} + .text_rt {text-align: right;} + .smaller {font-size:0.85em;} + .bigger {font-size:1.25em;} + .caption1 {font-weight: bold; font-size:1.75em; text-align: center;} + .caption2 {font-weight: bold; font-size:1.50em; text-align: center;} + .caption3 {font-weight: bold; font-size:1.15em; text-align: center;} + .caption4 {font-weight: bold; font-size:0.75em; text-align: center;} + .trans_notes {background:#d0d0d0; padding: 7px; border:solid black 1px;} + .chapt_hdr {text-align:center;font-size:1.75em; font-variant: small-caps; padding-top: 1em; padding-bottom:1em;} + .chapt_ttl {text-align:center; font-size:1.25em; padding-bottom:1em;} + .photo_cap {font-size:0.55em;} + .bold {font-weight: bolder;} + .figcenter {margin: 2em auto 2em auto; text-align: center; width: auto;} + .figcenter p { margin-top: 1.5em; } + span.text_lf {text-align: left; float: left;} + span.text_rt {text-align: right; float: right;} + +/* Footnotes */ + .footnotes {border: dashed 1px;} + .footnote {margin-left: 10%; margin-right: 10%; font-size: 0.9em;} + .footnote .label {position: absolute; right: 84%; text-align: right;} + .fnanchor { vertical-align: super; font-size: .8em; text-decoration: none;} + + </style> + </head> +<body> + + +<pre> + +The Project Gutenberg EBook of The Geological Story of the Isle of Wight, by +J. Cecil Hughes + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: The Geological Story of the Isle of Wight + +Author: J. Cecil Hughes + +Illustrator: Maud Neal + +Release Date: October 14, 2010 [EBook #33925] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK THE GEOLOGICAL STORY OF THE *** + + + + +Produced by Tom Cosmas and the Online Distributed +Proofreading Team at http://www.pgdp.net (This file was +produced from images generously made available by The +Internet Archive/American Libraries.) + + + + + + +</pre> + + +<div class="trans_notes"> +<div class="caption2">Transcriber's Notes</div> + +<p>With the exception of the changes noted below, the text in this file +is the same as that in the original printed version. These may include +alternate spelling from what may be common today (for example, +gneisse); punctuation and/or grammatical nuances. There are numerous +instances of words appearing as hyphenated versions and without a +hyphen (e.g., north-west and north west, south-east and south east, +etc.). Additionally, several missing periods were inserted; but are +not listed below. Lastly, the Index seems to be missing a few +references to page numbers and were left as originally printed.</p> +<a name="typos"></a> +<div class="caption2">Typographical Corrections</div> + +<table style="margin-left:auto; margin-right:auto;" summary="typos"> +<tr><td>Page 69: regious => <a href="#regions">regions</a></td></tr> +<tr><td>Page 101: sourrounding => <a href="#surrounding1">surrounding</a></td></tr> +<tr><td>Page 102: remains In the peat => <a href="#in">... in ...</a></td></tr> +<tr><td>Page 106: surounding => <a href="#surrounding2">surrounding</a></td></tr> +</table> + </div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Cover" id="Cover">[Cover]</a></span> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Cover_2" id="Cover_2">[Cover 2]</a></span> +<p> </p> +<p> </p> + +<div class="caption2">THE GEOLOGICAL STORY OF</div> +<p> </p> + +<div class="caption2">THE ISLE OF WIGHT.</div> +<p> </p> +<p> </p> + + +<p><span class='pagenum'><a name="Frontispiece" id="Frontispiece">[Frontispiece]</a></span></p> +<p> </p> + +<div class="center"> + <div style="width: 610px" class="figcenter"> + <img src="images/ph_0_gore_cl.png" width="600" height="368" title="Gore Cliff" alt="Gore Cliff" /><br /> + <div class="photo_cap"><span class="text_lf"><i>Photo by J. Milman Brown, Shanklin.</i></span> + <span class="smcap text_rt">Gore Cliff—Upper Greensand with Chert Beds</span></div> + </div> +</div> +<p> </p> +<p> </p> + + +<p><span class='pagenum'><a name="Page_i" id="Page_i">[Pg i]</a></span> + +<div class="center"> +<div class="caption2">The Geological Story<br /> +of the<br /> +Isle of Wight</div> +<br /> +<br /> +<div class="caption4">BY THE</div> +<div class="caption2">Rev. J. CECIL HUGHES, B.A.</div> +<br /> +<br /> +<i>With Illustrations of Fossils by</i><br /> +<div class="caption3"><i>MAUD NEAL</i></div> +<br /> +<br /> +<div class="caption4">LONDON:</div> +<br /> +<div class="caption3">EDWARD STANFORD, LIMITED</div> +<div class="caption4">12, 13, & 14 LONG ACRE, W.C. 2.</div> +<div class="caption3">1922</div> +</div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_ii" id="Page_ii">[Pg ii]</a></span></p> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_iii" id="Page_iii">[Pg iii]</a></span></p> + +<div class="caption2">PREFACE</div> + +<p>No better district could be chosen to begin the study of +Geology than the Isle of Wight. The splendid coast +sections all round its shores, the variety of strata within +so small an area, the great interest of those strata, the +white chalk cliffs and the coloured sands, the abundant +and interesting fossils to be found in the rocks, awaken +in numbers of those who live in the Island, or visit its +shores, a desire to know something of the story written +in the rocks. The Isle of Wight is classic ground of +Geology. From the early days of the science it has been +made famous by the work of great students of Nature, +such as Mantell, Buckland, Fitton, Sedgwick, Owen, +Edward Forbes, and others, who have carried on the study +up to the present day. Many of the strata are known to +geologists everywhere as typical; several bear the names +of the Island localities, where they occur; some—and +those not the least interesting—are not found beyond the +limits of the Island. Though studied for so many years, +there is no exhausting their interest: new discoveries are +constantly made, and new questions arise for solution. +To those who have become interested in the rocks of the +Island, and the fossils they have found in them, and who +wish to learn how to read the story they tell, and to know +something of that story, this book is addressed. It is intended +to be an introduction to the science of Geology, +based on the Geology of the Isle of Wight, yet leading +on to some glimpse of the history presented to us, when +we take a wider outlook still, and try to trace the whole +wondrous path of change from the world's beginning to +the present day.</p> + +<p><span class='pagenum'><a name="Page_iv" id="Page_iv">[Pg iv]</a></span> +I wish to express my warmest thanks to Miss Maud Neal +for the beautiful drawings of fossils which illustrate the +book, and to Professor Grenville A. J. Cole, F.R.S., for his +kindness in reading the manuscript, and for valuable +suggestions received from him. I have also to acknowledge +my indebtedness to Mr. H. J. Osborne White's new edition +of the <i>Memoir of the Geological Survey of the Isle of Wight</i>, +1921; and to thank Mr. J. Milman Brown, of Shanklin, +for the three photographs of Island scenery, showing +features of marked geological interest, and Mr. C. E. +Gilchrist, Librarian of the Sandown Free Library, for +kindly reading the proofs of the book.</p> + +<div class="text_rt">J. CECIL HUGHES.</div> +<br /> +Mar., 1922.<br /> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_v" id="Page_v">[Pg v]</a></span></p> +<a name="TOC"></a> +<div class="caption2">CONTENTS</div> + +<table width="100%" summary="Table of COntents"> +<tr><td colspan=2>Chap.</td><td class="text_rt">Page</td></tr> +<tr><td class="vtop text_rt">I.</td><td class="smcap"><a href="#Page_1">The Rocks and Their Story</a></td><td class="vbot text_rt">1</td></tr> +<tr><td class="vtop text_rt">II.</td><td class="smcap"><a href="#Page_10">The Structure of the Island</a></td><td class="vbot text_rt">10</td></tr> +<tr><td class="vtop text_rt">III.</td><td class="smcap"><a href="#Page_15">The Wealden Strata: The Land of the Iguanodon</a></td><td class="vbot text_rt">15</td></tr> +<tr><td class="vtop text_rt">IV.</td><td class="smcap"><a href="#Page_23">The Lower Greensand</a></td><td class="vbot text_rt">23</td></tr> +<tr><td class="vtop text_rt">V.</td><td class="smcap"><a href="#Page_29">Brook and Atherfield</a></td><td class="vbot text_rt">29</td></tr> +<tr><td class="vtop text_rt">VI.</td><td class="smcap"><a href="#Page_37">The Gault and Upper Greensand</a></td><td class="vbot text_rt">37</td></tr> +<tr><td class="vtop text_rt">VII.</td><td class="smcap"><a href="#Page_42">The Chalk</a></td><td class="vbot text_rt">42</td></tr> +<tr><td class="vtop text_rt">VIII.</td><td class="smcap"><a href="#Page_54">The Tertiary Era: The Eocene</a></td><td class="vbot text_rt">54</td></tr> +<tr><td class="vtop text_rt">IX.</td><td class="smcap"><a href="#Page_63">The Oligocene</a></td><td class="vbot text_rt">63</td></tr> +<tr><td class="vtop text_rt">X.</td><td class="smcap"><a href="#Page_70">Before and After: The Ice Age</a></td><td class="vbot text_rt">70</td></tr> +<tr><td class="vtop text_rt">XI.</td><td class="smcap"><a href="#Page_86">The Story of the Island Rivers; and How the Isle of Wight became an Island</a></td><td class="vbot text_rt">86</td></tr> +<tr><td class="vtop text_rt">XII.</td><td class="smcap"><a href="#Page_97">The Coming of Man</a></td><td class="vbot text_rt">97</td></tr> +<tr><td class="vtop text_rt">XIII.</td><td class="smcap"><a href="#Page_105">The Scenery of the Island: Conclusion</a></td><td class="vbot text_rt">105</td></tr> +</table> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_vi" id="Page_vi">[Pg vi]</a></span></p> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_vii" id="Page_vii">[Pg vii]</a></span></p> + +<div class="caption2">ILLUSTRATIONS OF FOSSILS</div> +<p> </p> + +<table width="100%" summary="Plates I-Description"> +<tr><td colspan=3 class="caption3"><a href="#Plate_I"><i>PLATE I.—Facing page 20.</i></a></td></tr> +<tr><td class="smcap vtop">Wealden</td><td class="vtop"> ... </td><td class="smcap">Cyrena Limestone<br>Vertebra of Iguanodon</td></tr> +<tr><td class="smcap vtop">Lower Greensand</td><td class="vtop"> ... </td><td class="smcap">Perna Mulleti<br />Meyeria Vectensis (Atherfield Lobster)<br />Panopæa Plicata<br />Terebratula Sella</td></tr> +</table> +<p> </p> +<table width="100%" summary="Plates II-Description"> +<tr><td colspan=3 class="caption3"><a href="#Plate_II"><i>PLATE II.—Facing page 23.</i></a></td></tr> +<tr><td class="smcap vtop">Lower Greensand</td><td class="vtop"> ... </td><td class="smcap">Trigonia Caudata<br />Trigonia Dædalea<br />Gervillia Sublanceolata</td></tr> +<tr><td class="smcap vtop">Upper Greensand</td><td class="vtop"> ... </td><td class="smcap">(Ammonite) Mortoniceras Rostratum<br />Nautilus Radiatus</td></tr> +</table> +<p> </p> +<table width="100%" summary="Plates III_Description"> +<tr><td colspan=3 class="caption3"><a href="#Plate_III"><i>PLATE III.—Facing page 45.</i></a></td></tr> +<tr><td class="smcap vtop">Lower Greensand</td><td class="vtop"> ... </td><td class="smcap">Thetironia Minor<br />Rhynchonella Parvirostris</td></tr> +<tr><td class="smcap vtop">Upper Greensand</td><td class="vtop"> ... </td><td class="smcap">(Pecten) Neithea Quinquecostata</td></tr> +<tr><td class="smcap vtop">Chalk</td><td class="vtop"> ... </td><td><span class="smcap">(Ammonite) Mantelliceras Mantelli<br />(Sea Urchins)<br /> Micraster Cor-Anguinum<br /> Echinocorys Scutatus</span> (Internal cast in flint)</td></tr> +</table> +<p> </p> + +<p><span class='pagenum'><a name="Page_viii" id="Page_viii">[Pg viii]</a></span></p> +<table width="100%" summary="Plates IV-Description"> +<tr><td colspan=3 class="caption3"><a href="#Plate_IV"><i>PLATE IV.—Facing page 61.</i></a></td></tr> +<tr><td class="smcap vtop">Eocene</td><td class="vtop"> ... </td><td class="smcap">Cardita Plarnicosta<br />Turritella Imbricataria<br />Nummulites Lævigatus<br />(Fusus) Leiostoma Pyrus</td></tr> +<tr><td class="smcap vtop">Oligocene</td><td class="vtop"> ... </td><td class="smcap">Limnæa Longiscata<br />Planorbis Euomphalus<br />Cyrena Semistriata</td></tr> +</table> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_ix" id="Page_ix">[Pg ix]</a></span></p> + +<div class="caption2">DIAGRAMS</div> + +<table width="100%" summary="ToC-Diagrams"> +<tr><td> </td><td colspan=2 class="text_rt">Facing page</td></tr> +<tr><td>1.</td><td class="smcap"><a href="#Fig_1">Coast, Sandown Bay</a></td><td class="text_rt">10</td></tr> +<tr><td>2.</td><td class="smcap"><a href="#Fig_2">Coast, Atherfield</a></td><td class="text_rt">29</td></tr> +<tr><td>3.</td><td class="smcap"><a href="#Fig_3">Coast, Whitecliff Bay</a></td><td class="text_rt">56</td></tr> +<tr><td class="vtop">4.</td><td class="smcap"><a href="#Fig_4">Section through Headon Hill and High Down. (Strata seen at Alum Bay)</a></td><td class="text_rt">58</td></tr> +<tr><td>5.</td><td class="smcap"><a href="#Fig_5">St George's Down</a></td><td class="text_rt">79</td></tr> +<tr><td>6, 7.</td><td class="smcap"><a href="#Fig_6">Development of River Systems</a></td><td class="text_rt">86</td></tr> +<tr><td>8.</td><td class="smcap"><a href="#Fig_8">The old Solent River</a></td><td class="text_rt">94</td></tr> +<tr><td>9.</td><td class="smcap"><a href="#Fig_9">Shingle at Foreland</a></td><td class="text_rt">79</td></tr> +</table> +<p> </p> + +<hr style="width: 35%; color:#000;" /> +<a name="PHOTOGRAPHS" id="PHOTOGRAPHS"></a> +<div class="caption2">PHOTOGRAPHS</div> + +<table width="100%" summary="ToC-Photos"> +<tr><td colspan=2 class="text_rt">Facing page</td></tr> +<tr><td>1. <span class="smcap"><a href="#Frontispiece">Gore Cliff.</a></span></td><td class="text_rt"><i>Frontispiece.</i></td></tr> +<tr><td>2. <span class="smcap"><a href="#Photo_1">Chalk at the Culver Cliffs.</a></span></td><td class="text_rt">46</td></tr> +<tr><td>3. <span class="smcap"><a href="#Photo_2">Chalk at Scratchell's Bay.</a></span></td><td class="text_rt">51</td></tr> +</table> +<p> </p> + +<hr style="width: 35%; color:#000;" /> +<table width="100%" summary="TOC-Geological Map"> +<tr><td class="bigger"><a href="#Geol_Map">GEOLOGICAL MAP OF THE ISLE OF WIGHT</a></td><td class="text_rt">112</td></tr> +</table> +<p> </p> +<p> </p> + +<span class='pagenum'><a name="Page_x" id="Page_x">[Pg x]</a></span> +<p> </p> +<p> </p> + +<span class='pagenum'><a name="Page_1" id="Page_1">[Pg 1]</a></span> + +<div class="chapt_hdr">Chapter I</div> +<div class="chapt_ttl">THE ROCKS AND THEIR STORY</div> + + +<p>Walking along the sea shore, with all its varied interest, +many must from time to time have had their attention +attracted by the shells to be seen, not lying on the sands, +or in the pools, but firmly embedded in the solid rock of +the cliffs and of the rock ledges which run out on to the +shore, and have, it may be, wondered sometimes how they +got there. At almost any point of the coast of the Isle +of Wight, in bands of limestone and beds of clay, in cliffs +of sandstone or of chalk, we shall have no difficulty in +finding numerous shells. But it is not only in the rocks +of the sea coast that shells are to be found. In quarries +for building stone and in the chalk pits of the downs we +see shells in the rock, and may often notice them in the +stones of walls and buildings. How did they get there? +The sea, we say, must once have been here. It must +have flowed over the land at some time. Now let us +think. We are going to read a wonderful story, written +not in books, but in the rocks. And it will be much more +valuable if we learn to read it ourselves, than if we are +just told what other people have made out. We know a +thing much better if we see the answers to questions for +ourselves than if we are told the answers, and take some +one else's word for it. And if we learn to ask questions +of Nature, and get answers to them, it will be useful in +all sorts of ways all through life. Now, look at the shells +in the rock of cliff and quarry. How are they there? +The sea cannot have just flowed over and left them. The +rock could not have been hard, as it is now, when they +<span class='pagenum'><a name="Page_2" id="Page_2">[Pg 2]</a></span> +got in. Some of the rocks are sandstone, much like the +sand on the sea shore, but they are harder, and their +particles are stuck together. Does sand on a sea shore +ever become hard like rock, so that shells buried in it are +found afterwards in hard rock? Now we are getting the +key to a secret. We are learning the way to read the +story of the rocks. How? In this way. Look around +you. See if anything like this is happening to-day. Then +you will be able to read the story of what happened long, +long ago, of how this world came to be as it is to-day. +We have asked a question about the sandstone. What +about the clays and the limestone? As before, what is +happening to-day? Is limestone being made anywhere +to-day, and are shells being shut up in it? Are shells in +the sea being covered up with clay,—with mud,—and more +shellfish living on the top of that; and then, are they, too, +being covered up? So that in years to come they will +be found in layers of clay and stone like those we have +been looking at in quarry and sea cliff?</p> + +<p>We have asked our questions. Now we must look +around, and see if we can find the answers. After it has +been raining heavily for two or three days go down to +the marshes of the Yar, and stand on one of the bridges +over the stream. We have seen it flowing quite clear on +some days. Now it is yellow or brown with mud. Where +did the mud come from? Go into a ploughed field with +a ditch by the side. Down the ditch the rain water is +pouring from the field away to the stream. It is thick +with mud. Off the ploughed field little trickles of water +are running into the ditch. Each brings earth from the +field with it. Off all the country round the rain is trickling +away, carrying earth into the ditches and on into the +stream, and the stream is carrying it down into the sea. +Now think. After every shower of rain earth is carried +off the land into the sea. And this goes on all the year +round, and year after year. If it goes on long enough—? +<span class='pagenum'><a name="Page_3" id="Page_3">[Pg 3]</a></span> +Look a long way ahead, a hundred years,—a thousand,—thousands +of years. We shall be talking soon of what +takes many thousands of years to do. Why, you say, if +it goes on long enough, all the land will be carried into +the sea. So it will be. So it must be. You see how the +world is changing. You will soon see how it has changed +already, what wonderful changes there have been. You +will see that things have happened in the world which +you never guessed till you began to study Geology.</p> + +<p>Now, let us go a bit further. What becomes of all the +mud the streams and rivers are carrying down into the +sea? Look at a stream coming steeply down from the +hills. How it rushes along, rolling pebbles against one +another, sweeping everything before it, clearing out its +channel, polishing the rocks, and carrying all it rubs off +down towards the sea. Now look at a river near its mouth +in flat lowland country. It flows now much slower; and +so it has not power to bear along all the material it swept +down from the hills. And so it drops a great deal; it is +always silting up its own channel, and in flood time +depositing fresh layers of mud on the flat meadow land,—the +alluvial flat,—through which it generally flows in the +last part of its course. But a good deal of sediment is +carried by the river out to sea. The water of the river, +moving slower as it enters the sea, has less and less power +to sweep along its burden of sand and mud, and it drops +it on the sea bottom,—first the bigger coarser particles +like the sand, then the mud; farther out, the finer particles +of mud drop to the bottom.</p> + +<p>During the exploring cruise of the <i>Challenger</i>, under the +direction of Sir Wyville Thomson, in 1872-6, the most +extensive exploration of the depths of the sea that has +been made up to the present time, it was found that +everything in the nature of gravel or sand was laid down +within a very few miles, only the finer muddy sediments +being carried as far as 20 to 50 miles from the land, the +<span class='pagenum'><a name="Page_4" id="Page_4">[Pg 4]</a></span> +very finest of all, under most favourable conditions, rarely +extending beyond 150, and never exceeding 300 miles +from land into the deep ocean. So gradually layer after +layer of sand and mud cover the sea bed round our coasts; +and shells of cockles and periwinkles, of crabs and sea +urchins, and other sea creatures that have lived on the +bottom of the sea are buried in the growing layers of +sand and mud. As layer forms on layer, the lower layers +are pressed together, and become more and more solid. +And so we have got a good way towards seeing the making +of clay and sandstone with shells in them, such as we +saw in the sea cliffs and the quarries.</p> + +<p>But it is not only rain and rivers that are wearing the +land away. All round the coasts the sea is doing the +same work. We see the waves beating against the shores, +washing out the softer material, hollowing caves into the +cliffs, eating away by degrees even the hardest rock, leaving +for a while at times isolated rocks like the Needles to +mark the former extension of the land. Most people see +for themselves the work of the sea, but do not notice so +much what the rain and the frost, the streams and the +rivers are doing. But these are wearing away the ground +over the whole country, while the sea is only eating away +at the coast line. So the whole of the land is being worn +away, and the sand and mud carried out into the sea, and +deposited there, the material of new land beneath the +waters.</p> + +<p>How do these beds rise up again, so that we find them +with their sea shells in the quarry? Well, we look at the +sea heaving up and down with the tides, and we think of +the land as firm and fixed. And yet the land also is continually +heaving up and down—very slowly,—far too +slowly for it to be noticed, but none the less surely. The +exact causes of this are not yet well understood, because +we know but little about the inside of the earth. The +deepest mine goes a very little way. We know that parts +<span class='pagenum'><a name="Page_5" id="Page_5">[Pg 5]</a></span> +of the interior are intensely hot. The temperature in a +mine becomes hotter, about 1°F. for every 60 ft. we go +down on the average. We know that there are great +quantities of molten rock in places, which, in a volcanic +eruption is poured out in sheets of lava over the land. +There are great quantities of water turned into steam by +the heat, and in an eruption the steam pours out of the +crater of the volcano like the clouds of steam out of the +funnel of a locomotive. The people who live about a +volcano are living, as it were, on the top of the boiler of +a steam engine; and their country is sometimes shaken +up and down like the lid of a kettle by the escaping steam. +In such a country the land is often changing its level. +A few miles from Naples at Pozzuoli, the ancient Puteoli, +may be seen columns of what appears to be an ancient +market hall, though it goes by the name of the Temple +of Serapis. About half way up the columns are holes +bored by boring shellfish, such as we may find on the shore +here at low tide. We see from this that since the building +was constructed in Roman times the land has sunk, and +carried the columns into the sea, and shellfish have bored +into them. Then the land has risen, and lifted the columns +out of the sea again.</p> + +<p>But it is not only in the neighbourhood of volcanoes +that the land is moving. Not suddenly and violently, +but slowly and gradually great tracts of land rise and sink. +Sometimes the land may remain for a long time nearly +stationary. The Southern coasts of England seem to +stand at much the same level as in the time of the +Romans 1,500 or 2,000 years ago. On the other hand there +is evidence which seems to show that the coast of Norway +has for some time been gradually rising.</p> + +<p>It was thought at one time that the interior of the +earth was liquid like molten lava, and that the land we +see was a comparatively thin crust over this like the crust +of a pie. But it is now believed for various mathematical +<span class='pagenum'><a name="Page_6" id="Page_6">[Pg 6]</a></span> +reasons, that the main mass of the earth is rigid as +steel. Still underneath the surface rocks there must +be a quantity of semi-fluid matter, like molten rock, and +on this the solid land sways about, as we see the ice on a +pond sway with the pressure of the skaters on it. So the +solid land, pressed by internal forces, rises and falls like +the elastic ice, sometimes sinking and letting the sea flow +over, then rising again, and bringing up the land from +beneath the sea.</p> + +<p>Again, as the heated interior of the earth gradually +cools by the radiation of the earth's heat into space, it +will tend to shrink away from the cooler rocks of the +crust. This then, sinking in upon the shrinking interior, +will be thrown into folds, like the skin on a shrivelled +apple. Seeing, as we often do, layers of rock thrown into +numerous folds, so as to occupy a horizontal space far less +than that in which they were originally laid down, we can +hardly resist the conclusion that shrinkage of the cooling +interior of the earth has been a chief cause of the greatest +movements of the surface, and of the lateral pressure we +so often find the strata to have undergone.</p> + +<p>As we study geology we shall find plenty to show that +the land does rise and fall, that where now is land the +sea has been, that land once stretched where now is sea, +though there is still much which is not well understood +about the causes of its movements. We have seen how +many of the rocks are made in the sea,—the sandstones +and the clays,—but there are two other kinds of rocks, +about which we must say a little. The first are the +Igneous rocks, which means rocks made by fire. These +rocks have solidified, most frequently in crystalline forms, +from a molten mass. Lava, which flows hot and fluid, +from a volcano, and cooling becomes a sheet of solid rock, +is an igneous rock. Some igneous rocks solidify under +ground under great pressure, and become crystalline +rocks such as granite. We shall not find these rocks in +<span class='pagenum'><a name="Page_7" id="Page_7">[Pg 7]</a></span> +the Isle of Wight. We should find them in Cornwall, +Wales, and Scotland; and, if we could go deep enough, +we should find some such rock as granite underneath the +other rocks all the world over. The other rocks, such as +the sandstones and clays, are called Sedimentary rocks, +because they are formed of sediment, material carried by +the sea and rivers, and dropped to the bottom. They +are also called Stratified rocks, because they are formed +of Strata, <i>i.e.</i>, beds or layers, as we see in cliff and +quarry.</p> + +<p>But we have seen another kind of rock,—the limestones. +In Sandown Bay towards the Culvers, bands of limestone +run through the dark clay cliffs, and broken fragments lie +on the shore, looking like pieces of paving stone. +Examining these we find that they are made up of shells, +one band of small oysters, the others of shells of other +kinds. You see how they have been made. There has +been an oyster bed, and the shells have been pressed +together, and somehow stuck together, so that they have +formed a layer of rock. They are stuck together in this +way. The atmosphere contains a small quantity of +carbonic dioxide, and the soil a larger quantity, the result +of vegetable decomposition. Rain water absorbs some +of it, and carries it into the rocks, as it soaks into the +ground. This gas has the property of combining with +carbonate of lime,—the material of which shells and +limestone are made. The bicarbonate of lime so formed +is soluble in water, which is not the case with the simple +carbonate. Water containing carbonic dioxide soaking +into a limestone rock or a mass of shells dissolves some of +the carbonate of lime, and carries it on with it. When it +comes to an open space containing air, some of the +carbonic dioxide is given off, leaving the insoluble carbonate +of lime again. So by degrees the hollows are filled up, and +a solid layer of rock is formed. Even while gathering in +the sea the shell-fragments may be cemented by the +<span class='pagenum'><a name="Page_8" id="Page_8">[Pg 8]</a></span> +deposit of carbonate of lime from sea-water containing +more of the soluble bicarbonate than it can hold.</p> + +<p>These limestones are examples of rocks which are said +to be of organic origin, that is to say, they are formed by +living things. Organic rocks may be formed by animal +or vegetable growth. Rocks of vegetable origin are seen +in the coals. A peat bog is composed of a mass of vegetable +matter, chiefly bog moss, which for centuries has +been growing and accumulating on the spot. At the +bottom of the bog will frequently be found trunks of oak, +or other trees, the remains of a forest of former days. The +wood has undergone chemical changes, has lost much of +its moisture, and often become very hard, as in bog oak. +Beds of coal have been formed by a similar process, on a +much vaster scale, and continued much longer. The +remains of ancient forests have been buried under sand +stones and other rocks, have undergone chemical change, +and been compressed into the hard solid mass we call +coal. Fossil wood, which has not reached the stage of +hard coal, but forms a soft brown substance, is called +lignite. This is of frequent occurrence in various strata +in the Isle of Wight.</p> + +<p>Of organic rocks of animal origin the most remarkable +are the chalk, of which we shall speak later, and the coral-reefs, +which are found in the warm waters of tropical seas. +Sailing over the South Pacific you will see a line of trees—coconut +trees chiefly—looking as if they rose up from the +sea. Coming nearer you see that they grow on a low +island, which rises only a few feet above the water. These +islands are often in the form of a ring, and look "like +garlands thrown upon the waters." Inside the ring is a +lagoon of calm water. Outside the heavy swell of the +Southern Ocean thunders on the coral shore. If a sounding +line be let down from the outer edge of the reef, it +will be found that the wall of coral goes down hundreds +of feet like a precipice. On an island in the Southern Sea, +<span class='pagenum'><a name="Page_9" id="Page_9">[Pg 9]</a></span> +Funafuti, a deep boring has been made 1,114 ft. deep. +As far as the boring went all was coral. All this mass of +coral is formed by living things,—polyps they are called. +They are like tiny sea anemones, only they grow attached +to one another, forming a compound animal, like a tree +with stem and branches, and little sea anemones for +flowers. The whole organism has a sort of shell or skeleton, +which is the coral. Blocks are broken off by the waves, +and ground to a coral mud, which fills up the interstices +of the coral; and as more coral grows above, the lower +part of the reef becomes, by pressure and cementing, a solid +coral limestone. Once upon a time there were coral +islands forming in a sea, where now is England. These +old coral reefs form beds of limestone in Devon, Derbyshire, +and other parts of England. In the Isle of Wight +we have no old coral reefs, but we shall easily find fossil +corals in the rocks. They helped to make up the rocks, +but there were not enough here to make reefs or islands +all of coral.</p> + +<p>The great branching corals that form the reefs can only +live in warm waters. So we see that when corals were +forming reefs where now is England the climate must +have been warm like the tropics. That is a story we +shall often read as we come to hear more about the rocks. +We shall find that the climate has often been quite warm +as the tropics are now: and we shall also read another +wonderful story of a time when the climate was cold like +the Arctic regions. +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_10" id="Page_10">[Pg 10]</a></span></p> + +<div class="chapt_hdr">Chapter II.</div> +<div class="chapt_ttl">THE STRUCTURE OF THE ISLAND.</div> + +<p>The best place to begin the study of the Geology of the Isle +of Wight is in Sandown Bay. North of Sandown, beyond +the flat of the marshes, are low cliffs of reddish clay, which +has slipped in places, and is much covered by grass. At +low tide we shall see the coloured clays on the shore, unless +the sand has covered them up. Variegated marls they +are called—<i>marl</i> means a limy clay, <i>loam</i> a sandy clay; +and very fine are the colours of these marls, rich reds and +purples and browns. Beyond the little sea wall below +Yaverland battery we come to a different kind of clay +forming the cliff. It is in thin layers. Clay in thin +layers like this is called <i>shale</i>. Some of these shales are +known as paper shales, for the layers are thin almost like +the leaves of a book. The junction of the shales with the +marls is quite sharp, and we see that the shales rest on the +coloured marls, not horizontally, but sloping down towards +the North. Bands of limestone and sandstone running +through the shales, and a hard band of brown rock which +runs out on the shore as a reef, slope in the same direction. +As we pass on by the Red Cliff to the White Cliffs we +notice that the strata slope more steeply the further North +we go. We have seen that these strata were laid down +layer by layer at the bottom of the sea. If we find a lot +of things lying one on top of another, we may generally +conclude that the ones at the bottom were put there first, +then the next, and so on to the top. And this will +generally be true with regard to the rocks. The lowest +rocks must have been laid down first, then the next, and +<span class='pagenum'><a name="Page_11" id="Page_11">[Pg 11]</a></span> +so on. But these layers of shale with shells in them, and +layers of limestone made of shells, must have been laid +down at first fairly flat on the sea floor; but as they +were upheaved out of the sea they have been tilted, so +that we now see them in an inclined position. And when +we come to the chalk, we should see, if we looked at the +end of the Culver Cliffs from a boat, that the lines of +black flints that run through the chalk are nearly vertical. +The strata there have been tilted up on end.</p> +<p> </p> +<p> </p> + +<a name="Fig_1" id="Fig_1"></a> +<div class="text_rt smcap">Fig. 1</div> + +<div class="center"> + <div style="width: 598px" class="figcenter"> + <img src="images/fig_1.png" width="598" height="94"title="Fig. 1 Diagram Of Coast, Sandown Bay, Dunnose To Culver Cliff." alt="Fig. 1" /> + </div> + <table class="smaller" summary="Strata List"> + <tr><td colspan=7>DIAGRAM OF COAST, SANDOWN BAY, DUNNOSE TO CULVER CLIFF.</td></tr> + <tr><td> </td><td>W</td><td><i>Wealden.</i></td><td> </td><td>g</td><td><i>Gault.</i></td><td> </td></tr> + <tr><td> </td><td>P</td><td><i>Perna Bed.</i></td><td> </td><td>UG</td><td><i>Upper Greensand.</i></td><td> </td></tr> + <tr><td> </td><td>LG</td><td><i>Lower Greensand.</i></td><td> </td><td>C</td><td><i>Chalk.</i></td><td> </td></tr> + <tr><td> </td><td>Cb</td><td><i>Clay Bands.</i></td><td> </td><td>Sc</td><td><i>Shanklin Chine.</i></td><td> </td></tr> + <tr><td> </td><td>S</td><td><i>Sandrock and Carstone.</i></td><td> </td><td>Lc</td><td><i>Luccombe Chine.</i></td><td> </td></tr> + </table> +</div> +<p> </p> +<p> </p> + +<p>In describing how strata lie, we call the inclination of +the strata from the horizontal the <i>dip</i>. The direction of +a horizontal line at right angles to that of the dip is called +the <i>strike</i>. If we compare the sloping strata to the roof +of a house, a line down the slope of the roof will mark the +direction of the dip, the ridge of the roof that of the strike. +The strata we are considering dip towards the North; +the line of strike is East and West.</p> + +<p>Returning towards Sandown we see the strata dipping +less and less steeply, till near the Granite Fort the rocks +on the shore are horizontal. Continuing our walk past +Sandown to Shanklin we pass the same succession of rocks +we have been looking at, but in reverse order, and sloping +the other way. It is not very easy to see this at first, for +so much is covered by building; but beyond Sandown we +see Sandstone Cliffs like the Red Cliff again, the strata +dipping gently now to the south, and in the downs above +Shanklin we see the chalk again. So we have the same +strata north and south of Sandown, forming a sort of +arch. But the centre of the arch is missing. It must +have been cut away. We saw that the land was all being +eaten away by rain and rivers. Now we see what they +have done here. Go up on to the Downs, and look over +the central part of the Island. We see two ranges of +downs running from east to west,—the Central Downs of +the Island, a long line of chalk down 24 miles from the +Culver Cliff on the east to the Needles on the west; and +<span class='pagenum'><a name="Page_12" id="Page_12">[Pg 12]</a></span> +the Southern Downs along the South Coast from +Shanklin to Chale. In the Central Downs the chalk +rises nearly vertically, and turns over in the beginning +of an arch towards the South. Then comes a big gap, +and the chalk appears again in the Southern Downs +nearly horizontal, sloping gently to the south. The +chalk was once joined right across the central hollow, +where now we see the villages of Newchurch, Godshill, +and Arreton. All that enormous mass of rock that once +filled the space between the downs has been cut away by +running water.</p> + +<p>An arch of strata like this <img src="images/cap.png" width="12" height="12" border="0" alt="cap" title="anticline" />, such as the one we are +looking at, is called an <i>anticline</i>. When the arch is reversed, +like this <img src="images/cup.png" width="12" height="12" border="0" alt="cup" title="syncline" />, it is called a <i>syncline</i>. Looking north +from the Central Downs over the Solent we are looking +at a syncline. The chalk, which dips down at the Culvers +and along the line of the Central Downs, runs like a trough +under the Solent, and rises again, as we see it on the other +side, in the Portsdown Hills.</p> + +<p>We might suppose the top of an anticlinal arch would +be the highest part of the country; that, even if rain +and running water have worn the country down, that +would still stand highest, and be worn down least. But +there are reasons why this need not be so. For one thing, +when the horizontal strata are curved over into an arch, +they naturally crack just at the top of the curve, so <img src="images/curve_2_v.png" width="62" height="12" border="0" alt="curve with two craks near top" title="curve with two craks near top" /> and into the cracks the rain gets, and so a stream is +started there, which cuts down and widens its channel, +and so eats the land away. Again, the rising land only +emerges gradually from the sea, and the sea may cut off +the top of the arch before it has risen out of its reach. +Moreover on the higher land the fall of rain and snow is +greater, and the frosts are more severe; so that it is just +<span class='pagenum'><a name="Page_13" id="Page_13">[Pg 13]</a></span> +there that the forces wearing down the land are most +effective.</p> + +<p>We must notice another thing which happens when +rocks are being upheaved and bent into curves. The +strain is very great, and sometimes the strata crack and +one side is pushed up more than the other. These cracks +are called <i>faults</i>. At Little Stairs, about half way +between Sandown and Shanklin, two or three faults may +be seen in the cliff. The effect of two of the faults may +be easily seen by noticing the displacement of a band +of rock stained orange by water containing iron. The +strata are thrown down towards the north about 8 ft. +A third fault, the effect of which is not so evident at first +sight, throws the strata down roughly 50 ft. to the south. +These are only small faults, but sometimes faults occur, +in which the strata have been moved on opposite sides of +the fault thousands of feet away from one another. We +might think we should see a wall of rock rising up on the +surface of the ground where a fault occurs; but the faults +have mostly taken place ages ago; and, when they do +happen, the rocks are generally moved only a little way +at a time. Then after a while another push comes on the +rocks, and they shift again at the same place, and go a bit +further. All this time frost and rain and rivers are working +at the surface, and planing it down; so that the unevenness +of the surface caused by faults is smoothed away; +and so even a great fault does not show at the surface.</p> + +<p>As we follow the Sandown anticline westward it gradually +dies away, the upheaved area being actually a long +oval—what we may call a turtle-back. As the Sandown +anticline dies out, it is succeeded by another a little +further south, the Brook anticline. There are in fact a +series of these east and west anticlines in the Island and +on the adjacent mainland, caused by the same earth +movement. As a consequence of the arching of the strata +we find the lowest beds we saw in Sandown Bay running +<span class='pagenum'><a name="Page_14" id="Page_14">[Pg 14]</a></span> +out again on the west of the Island in Brook Bay, and a +general correspondence of the strata on the east and west +of the Island; while, as we travel from Sandown or Brook +northward to the Solent, we come to continually more +recent beds overlying those which appear to the south +of them.</p> + +<p>When, as in the south side of our central downs, the +strata are sharply cut away by denudation, we call this +an <i>escarpment</i>. The <a href="#Fig_1">figure</a> shows the structure of the +Sandown anticline we have described. We must now +examine the rocks more closely, beginning with the lowest +strata in the Island, and try to read the story they have +to tell. +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_15" id="Page_15">[Pg 15]</a></span></p> + +<div class="chapt_hdr">Chapter III</div> + +<div class="chapt_ttl">THE WEALDEN STRATA: THE LAND OF THE IGUANODON</div> + +<p>The lowest strata in the Isle of Wight are the coloured +marls and blue-grey shales we have already observed in +Sandown Bay, which run through the Island to Brook +Bay. They are known as the Wealden Strata, because +the same strata cover the part of Kent and Sussex called +the Weald. They consist of marls and shales with bands +of sandstone and limestone. The marls and shales in +wet weather become very soft, and flow out on to the +shore, causing large slips of land.<a name="FNanchor_A_1" id="FNanchor_A_1"></a><a href="#Footnote_A_1" class="fnanchor">[1]</a> Now, what we want +to find out is what the world was like ages ago, when +these Wealden Strata were being formed. We have +learnt something of how clays and sandstones and limestones +are formed: to learn more we must see what sort +of fossils we can find in these rocks. "Fossil" means +something dug up; and the word is generally used for +remains of animals or plants which we find buried in the +rocks. We have seen shells in these strata. These we +must examine more closely. And as we walk on the shore +we shall find other fossils. In the marls and shales exposed +on the shore we are pretty sure to see pieces of wood, +black as coal, sometimes quite large logs, often partly +covered with shining iron pyrites. Perhaps you say—I +hope you do—there must have been land not far away +when these marls and shales were forming. Always try +to see what the things we find have to tell us. The sort +of place where we should be most likely to find wood +floating in the sea to-day would be near the mouth of a +great river like the Mississippi or the Amazon,—rivers +which bring down numerous logs of wood from the forest +country through which they flow.</p> + +<p><span class='pagenum'><a name="Page_16" id="Page_16">[Pg 16]</a></span> +Examine the shales and limestone bands. On the +surface of some of the paper-shales are numbers of small +round or oval white spots. They are the remains of shells +of a very minute crustacean, Cypris and Cypridea, from +which the shales are known as Cyprid shales. In other +bands of shale are quantities of a bivalve shell called +<i>Cyrena</i>. There is a band of limestone made up of Cyrena +shells, containing also little roundish spiral shells called +<i>Paludina</i>.<a name="FNanchor_A_2" id="FNanchor_A_2"></a><a href="#Footnote_A_2" class="fnanchor">[2]</a> This limestone resembles that called Sussex +or Petworth Marble, which is mainly composed of shells +of Paludina, but some layers also contain bivalve shells. +It is hard enough to take a good polish, and may be seen, +like the similar Purbeck marble, in some of our grand old +churches. Another band of limestone running through +the shales is made up of small oysters (<i>Ostrea distorta</i>).</p> + +<p>We shall see fossil shells best on the <i>weathered</i> surfaces +of rocks, <i>i.e.</i>, surfaces which have been exposed to the +weather. One beginning geological study will probably +think we shall find fossils best by looking at fresh broken +surfaces of rock. This is not so. If you want to find +fossils, look at the rock where it has been exposed to the +weather. The action of the weather—rain, carbonic +dioxide in the rain water, etc.—is to sculpture the surface +of the rock, so that the fossils stand out in relief. A +weathered surface is often seen covered with fossils, when +a new broken one shows none at all.</p> + +<p>Many of the shells in the limestones are very like shells +which are found at the present day. We must know +<span class='pagenum'><a name="Page_17" id="Page_17">[Pg 17]</a></span> +where they are found now. Well, these Paludinas are a +kind of freshwater snail; and, in fact, all the shells we +find in the Wealden strata are freshwater shells, till we +come near the top, and find the oysters, which live in +salt or brackish water. There were quantities in Brading +Harbour in old days, before it was reclaimed from the sea. +Now, this is a very important point, that our Wealden +shells are freshwater shells. For what does it tell us? +Why, we see that the first strata we have come to examine +were not laid down in the sea at all. Then where were +they formed? They seem to be the Delta of a great +river, long since passed away, like the Nile, the Amazon, +or the Niger at the present day. When these great rivers +near the sea, they spread out in many channels, and +deposit the mud they have brought down over a wide +area shaped like a V, or like the Greek letter <a name="Greek_D">Δ</a>). +Hence we speak of the Delta of the Nile. Some river +deltas are of immense size. That of the Niger, for +instance, is 170 miles long, and the line where it meets +the sea is 300 miles long. Our old Wealden river must +have been a great river like the Niger, for the Wealden +strata stretch,—often covered up for a long way by later +rocks, then appearing again,—as far as Lulworth on the +Dorset coast to the west, into Buckinghamshire on the +north, while to the north east they not only cover the +Weald, but pass under the Straits of Dover into Belgium, +and very similar strata are found in Westphalia and +Hanover. The ancient river delta must have been 200 +miles or more across.</p> + +<p>You must not think this great river flowed in the +Island of England as it is to-day. England was being +made then. This must have been part of a great continent +in those days, for such a great river to flow through, +and form a delta of such size. We cannot tell quite what +was the course of this river. But to the north of where +we are now must have stretched a great continent, with +<span class='pagenum'><a name="Page_18" id="Page_18">[Pg 18]</a></span> +chains of lofty mountains far away, from which the head +waters of the river flowed. Near its mouth the river +broke up into many streams, separated by marsh land; +while inside the sand banks of the sea shore would be +large lagoons as in the Nile delta at the present day. +In these waters lived the shellfish whose shells we are +finding. And flowing through great forests the river carried +down with it logs of wood and whole trees, and left them +stuck in the mud near its mouths for us to find to-day.</p> + +<p>What kind of trees grew in the country the river came +from? Well, there were no oaks or beeches, no flowering +chestnuts or apples or mays. But there were great +forests of coniferous trees; that is trees like our pines +and firs, cedars and yews, and araucarias; and there were +cycads—a very different kind of tree, but also bearing +cones—which you may see in a greenhouse in botanical +gardens. They have usually a short trunk, sometimes +nearly hemispherical, with leaves like the long leaves of a +date palm. They are sometimes called sago trees, for +the trunk has a large pith, which, like some palms, gives +us sago. Stems of cycads, covered with diamond-shaped +scars, where the leaf stalks have dropped off, are found +in the Wealden deposits. Most of the wood we find is +black and brittle. Some, however, is hard as stone, where +the actual substance of the wood has been replaced by +silica, preserving beautifully the structure of the wood. +Specially noteworthy are fragments of a tree called +<i>Endogenites</i> (or <i>Tempskya</i>) <i>erosa</i>, because it was at first +supposed to belong to the endogens,—the class to which +the palm bamboo belong; it is now considered to be +a tree-fern. Many specimens of this wood are remarkably +beautiful, when polished, or in their natural condition. +Here, by the way, it may be well to explain how +we name animals and plants scientifically. We have +English names only for the commoner varieties. So we +have to invent names for the greater number of living and +<span class='pagenum'><a name="Page_19" id="Page_19">[Pg 19]</a></span> +extinct animals and plants. And the best way is found +to be this. We give a name, generally formed from the +Latin—or the Greek—to a group of animals or plants, +which closely resemble one another; the group we call +a <i>genus</i>. Then for the <i>species</i>, the particular kind of +animal or plant of the group, we add a second name to +the first. Thus, if we are studying the apple and pear +group of fruit trees, we call the general name of the group +<i>Pyrus</i>. Then the crab apple is <i>Pyrus malus</i>, the wild +pear <i>P. communis</i>, and so on. So that when you arrange +any of your species, and put down the scientific names, +you are really doing a bit of classification as well. You +are arranging your specimens with their nearest relations.</p> + +<p>To return to our ancient river. With the logs and +trunks of trees, which the river brought down, came +floating down also the bodies of animals, which had lived +in the country the river flowed through. What kind of +animals? Very wonderful animals, some of them, not +like any living creature that lives to-day. By the time +they reached the mouth of the river the bodies had come +to pieces, and their bones were scattered about the river +mouth. On the shore where we are walking we may find +some of these bones. But it is rather a chance whether +we find any in any one walk we take. The best time to +find them is when rough seas in winter have washed some +out of the clay, and left them on the shore. It is only +rarely that large bones are found here; but you should +be able to find some small ones fairly often. The bones +are quite as heavy as stone, for all the pores and cavities +have been filled with stone, generally carbonate of lime, +in the way we explained in describing the formation of +beds of limestone. This makes them quite different from +any present-day bones that may happen to lie on the +shore. So that you cannot mistake them, if once you +have seen them. They are bones of great reptiles,—the +class of creatures to which lizards and crocodiles belong. +<span class='pagenum'><a name="Page_20" id="Page_20">[Pg 20]</a></span> +But these were much larger than crocodiles, and quite +peculiar in their appearance. The principal one was the +Iguanodon. He stood on his hind legs like a kangaroo, +with a great thick tail, which may have helped to support +him. When full grown he stood about 14 ft. high. You +may find on the shore vertebræ, <i>i.e.</i>, joints of the backbone, +sometimes large, sometimes quite small if they come +from the end of the tail. I have found several here about +5 inches long by 4 or 5 across. A few years ago I found +the end of a leg bone almost a foot in diameter. Dr. +Mantell, a great geological explorer in the days when these +reptiles were first discovered about 80 years ago, estimated +from the size of part of a bone found in Sandown Bay +that one of these reptiles must have had a leg 9 ft. long. +It was a long time after the bones of these creatures were +first found before it was known what they really looked +like. The animals lived a long way from here, and by +the time the river had washed them down to its mouth +the skeletons were broken up, and the bones scattered. +At last a discovery was made, which told us what the +animals were like. In a coal mine at Bernissart in +Belgium the miners found the coal seam they were following +suddenly come to an end, and they got into a mass +of clay. After a while it was seen what had happened. +They had struck the buried channel of an old river, which +in the Wealden days had flowed through and cut its +channel in the coal strata, which are much older still +than the Wealden. And in the mud of the ancient buried +river what should they come upon but whole skeletons +of Iguanodons. In the days of long ago the great beasts +had come down to the river to drink, and had got "bogged" +in the soft clay. The skeletons were carefully got out, +and set up in the Museum at Brussels. Without going +so far as that, you may see in the Natural History Museum +in London, or the Geological Museum at Oxford, a +facsimile of one of these skeletons, large as life, and have +some idea of the sort of beast the Iguanodon was. I +should tell you why he was so named. Before it was +known what he was like in general form, it was found that +his teeth, which are of a remarkable character, were +similar to those of the Iguana, a little lizard of the West +Indies. So he was called Iguanodon,—an animal with +teeth like the Iguana (fr. <i>Iguana</i>, and Gk. <a name="Greek_odous">όδούς</a> g. <a name="Greek_odontos">όδόντυς</a> +a tooth). He was quite a harmless beast, though he was +so large. He was a vegetarian. There were other great +reptiles, more or less like him, which were also vegetable +feeders. But there were also carnivorous reptiles, +generally smaller than the herbivorous, whose teeth tell +us that they preyed on other animals.</p> +<p> </p> +<p> </p> + +<a name="Plate_I" id="Plate_I"></a> +<div class="smcap text_rt">PL. I</div> + +<table width="100%" class="center" summary="Plate I-Images"> +<tr><td><img src="images/pl_i_perna.png" width="160" height="175" title="" alt="" /><br /><span class="smaller smcap">Perna Mulleti</span></td><td><img src="images/pl_i_meyeria.png" width="181" height="106" title="" alt="" /><br /><span class="smaller smcap">Meyeria Vectensis<br />(Atherfield Lobster)</span></td></tr> + +<tr><td><img src="images/cleardot.png" width="2" height="32" title=" " alt=" " /><br /><img src="images/pl_i_panopaea.png" width="159" height="85" title="" alt="" /><br /><span class="smaller smcap">Panopæa Plicata</span></td><td><a name="Terebratula"></a><img src="images/pl_i_terebratula.png" width="81" height="81" title="" alt="" /><br /><span class="smaller smcap">Terebratula Sella</span></td></tr> + +<tr><td><img src="images/cleardot.png" width="2" height="32" title=" " alt=" " /><br /><img src="images/pl_i_cyrena.png" width="202" height="172" title="" alt="" /><br /><span class="smaller smcap">Cyrena Limestone</span></td><td><img src="images/pl_i_iguanodon.png" width="176" height="164" title="" alt="" /><br /><span class="smaller smcap">Iguanodon Vertebra</span></td></tr> +</table> + +<div class="caption4">WEALDEN AND LOWER GREENSAND</div> + +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_21" id="Page_21">[Pg 21]</a></span> +Those were the days of reptiles. Now the earth is the +domain of the mammalia. But then great reptiles like +the Iguanodon wandered over the land; great marine +reptiles, such as the Plesiosaurus, swam the waters; and +wonderful flying reptiles, the Pterodactyls, flew the air. +Some species of these were quite small, the size of a rook: +one large species found in the Isle of Wight had a spread +of wing of 16 feet. Imagine this strange world,—its +forests with pines and monkey puzzles and cycads,—ferns +also, of which many fragments are found,—its great +reptiles and little reptiles, on land, in the water and the +air. Were there no birds? Yes, but they were rare. +From remains found in Oolitic strata,—somewhat older +than the Wealden,—we know that birds were already +in existence; and they were as strange as anything else. +For they had jaws with teeth like the reptiles. They had +not yet adopted the beak. And instead of all the tail +feathers starting from one point, as in birds of the present +day, these ancient birds had long curving tails like reptiles, +with a pair of feathers on each joint. Birds of similar but +slightly more modern type have been found in Cretaceous +strata (to which the Wealden belongs) in America, but so +far not in strata of this age in Britain.</p> + +<span class='pagenum'><a name="Page_22" id="Page_22">[Pg 22]</a></span> +<p>Among other objects of interest along this Wealden +shore may be noticed a curious transformation which has +affected the surface of some of the shell limestones after +they were formed, which is known as cone-in-cone structure. +It has quite altered the outer layer of the rock, so that all +trace of the shells of which it consists is obliterated. Numerous +pieces of iron ore from various strata lie on the shore. +Through most of English history the Weald of Kent and +Sussex was the great iron-working district of England. +The ore from the Wealden strata was smelted by the +help of charcoal made from the woods that grew there, +and gave the district its name;—for <i>Weald</i> means "forest." +This industry gradually ceased, as the much larger supplies +of iron ore found near the coal in the mines of the North +of England came to be worked. Iron pyrites, sulphide of +iron in crystalline form, was formerly collected on the +Sandown shore, and sent to London for the manufacture +of sulphuric acid. This mineral is often found encrusting +fossil wood. It also occurs as rounded nodules (mostly +derived from the Lower Chalk) with a brown outer coat, +and often showing a beautiful radiated metallic structure, +when broken. (This form is called marcasite.)</p> + +<p>As we walk by the edge of the water, we shall see what +pretty stones lie along the beach. When wet with the +ripples many look like polished jewels. Some are agates, +bright purple and orange in colour, some clear translucent +chaldedony. We shall have more to say about these +later on. They do not come from the Wealden, but from +beds of flint gravel, and are washed along the shore. But +there are also jaspers from the Wealden. These are +opaque, generally red and yellow. There are also pieces +of variegated quartz, and other beautiful pebbles of +various mineral composition. These are stones from older +rocks, which have been washed down the Wealden rivers, +and buried in the Wealden strata, to be washed out again +after hundreds of thousands of years, and rolled about +on the shore on which we walk to-day.</p> + +<div class="footnote"><p><a name="Footnote_A_1" id="Footnote_A_1"></a><a href="#FNanchor_A_1"><span class="label">[1]</span></a> Blue clays of various geological age, which in wet weather +become semi-liquid, and flow out on to the shore, are known in the +Island by the local name of <i>Blue Slipper</i>.</p></div> + +<div class="footnote"><p><a name="Footnote_A_2" id="Footnote_A_2"></a><a href="#FNanchor_A_2"><span class="label">[2]</span></a> The name now adopted is <i>Viviparus</i>. There is also a band of +ferruginous limestone mainly composed of <i>Viviparus</i>.</p></div> +<p> </p> +<p> </p> + +<a name="Plate_II" id="Plate_II"></a> +<div class="smcap text_rt">PL. II</div> + +<table width="100%" class="center" summary="Plate II-Images"> +<tr><td><img src="images/pl_ii_trigonia_c.png" width="169" height="119" title="Trigonia Caudata" alt="Trigonia Caudata" /><br /><span class="smaller smcap">Trigonia Caudata</span></td><td><img src="images/pl_ii_trigonia_d.png" width="143" height="113" title="Trigonia Daedalea" alt="Trigonia Daedalea" /><br /><span class="smaller smcap">Trigonia Dædalea</span></td></tr> + +<tr><td colspan=2><img src="images/cleardot.png" width="2" height="32" title=" " alt=" " /><br /><img src="images/pl_ii_gervillia.png" width="222" height="64" title="Gervillia Sublanceolata" alt="Gervillia Sublanceolata" /><br /><span class="smaller smcap">Gervillia Sublanceolata</span><br /><img src="images/cleardot.png" width="2" height="32" title=" " alt=" " /></td></tr> + +<tr><td><img src="images/pl_ii_ammonite.png" width="207" height="204" title="Ammonite" alt="Ammonite" /><br />(<span class="smaller smcap">Ammonite)<br />Mortoniceras Rostratum</span></td><td><img src="images/pl_ii_nautilus.png" width="179" height="174" title="" alt="" /><br /><span class="smaller smcap">Nautilus Radiatus</span></td></tr> +</table> + +<div class="caption4">LOWER AND UPPER GREENSAND</div> +<p> </p> +<p> </p> + + + +<p><span class='pagenum'><a name="Page_23" id="Page_23">[Pg 23]</a></span></p> + +<div class="chapt_hdr">Chapter IV</div> + +<div class="chapt_ttl">THE LOWER GREENSAND</div> + + +<p>For ages the Wealden river flowed, and over its vast delta +laid down its depth of river mud. The land was gradually +sinking; for continually strata of river mud were laid +down over the same area, all shallow-water strata, yet +counting hundreds of feet in thickness in all. At last a +change came. The land sank more rapidly, and in over +the delta the sea water flowed. The sign of coming change +is seen in the limestone band made up of small oysters +near the top of the Wealden strata. Marine life was +beginning to appear.</p> + +<p>Above the Wealden shales in Sandown Bay may be +seen a band of brown rock. It is in places much covered by +slip, but big blocks lie about the shore, and it runs out to +sea as a reef before we come to the Red Cliff. The blocks +are seen to consist of a hard grey stone, but the weathered +surfaces are soft and brown. They are full of fossils, all +marine, sea shells and corals. The sea has washed in +well over our Wealden delta, and with this bed the next +formation, the Lower Greensand, begins. The bed is +called the Perna bed, from a large bivalve shell (<i>Perna +mulleti</i>) frequently to be found in it, though it is difficult +to obtain perfect specimens showing the long hinge of +the valve, which is a marked feature of the shell. Among +other shells are a large round bivalve <i>Corbis</i> (<i>Sphæra</i>) +<i>corrugata</i>, a flatter bivalve <i>Astarte</i>,—and a smaller oblong +shell <i>Panopæa</i>,—also a peculiar shell of triangular form, +<i>Trigonia</i>,—one species <i>T. caudata</i> has raised ribs running +across it, another <i>T. dædalea</i> has bands of raised spots. +<span class='pagenum'><a name="Page_24" id="Page_24">[Pg 24]</a></span> +A pretty little coral, looking like a collection of little stars, +<i>Holocystis elegans</i>, one of the Astræidæ, is often very +sharply weathered out.</p> + +<p>Above the Perna bed lies a mass of blue clay, weathering +brown, called the Atherfield clay, because it appears +on a great scale at Atherfield on the south west of the +Island. It is very like the clay of the Wealden shales, +but is not divided into thin layers like shale.</p> + +<p>Next we come to the fine mass of red sandstone which +forms the vertical wall of Red Cliff. Not many fossils +are to be found in these strata. Let us note the beauty +of colouring of the Red Cliff—pink and green, rich orange +and purple reds. And then let us pass to the other side +of the anticline, and walk on the shore to Shanklin. Here +we see the red sandstone rocks again, but now dipping +to the south. You probably wonder why these red cliffs +are called Greensand. But look at the rocks where they +run out as ledges on the shore towards Shanklin. Here +they are dark green. And this is really their natural +colour. They are made of a mixture of sand and clay +coloured dark green by a mineral called glauconite. +Grains of glauconite can easily be seen in a handful of +sand,—better with a magnifying glass. This mineral is +a compound of iron, with silica and potash, and at the +surface of the rock it is altered chemically, and oxide of +iron is formed—the same thing as rust. And that colours +all the face of the cliff red. The iron is also largely responsible +for our finding so few fossils in these strata. +By chemical changes, in which the iron takes part, the +material of the shells is destroyed.<a name="FNanchor_A_3" id="FNanchor_A_3"></a><a href="#Footnote_A_3" class="fnanchor">[3]</a> Near Little Stairs +hollows in the rock may be seen, where large oyster shells +have been. In some you may find a broken piece of shell, +but the shells have been mostly destroyed. Nearer +<span class='pagenum'><a name="Page_25" id="Page_25">[Pg 25]</a></span> +Shanklin we shall find large oysters, <i>Exogyra sinuata</i>, in the +rock ledges exposed at low tide. Some are stuck together in +masses. Evidently there was an oyster bank here. And +here the shells have not been destroyed like those in the cliff.</p> + +<p> +From black bands in the cliff water full of iron oozes +out, staining the cliff red and yellow and orange, and +trickling down, stains the flint stones lying on the shore +a bright orange. At the foot of the cliff you may sometimes +see what looks like a bed of conglomerate, <i>i.e.</i>, a +bed of rounded pebbles cemented together. This does +not belong to the cliff, but is made up of the flint pebbles +on the shore, and the sand in which they lie, cemented +into a solid mass by the iron in the water which has +flowed from the cliff. It is a modern conglomerate, and +shows us how old conglomerates were formed, which we +often find in the various strata. The cement, however, +in these is not always iron oxide. It may be siliceous or +of other material. The iron-charged water is called +chalybeate; springs at Shanklin and Niton at one time +had some fame for their strengthening powers. The +strata we have been examining are known as the Ferruginous +sands, <i>i.e.</i>, iron sands (Lat. <i>ferrum</i>, "iron"). +Beyond Shanklin is a fine piece of cliff. Look up at it, +but beware of going too close under it. The upper part +consists of a fine yellow sand called the Sandrock. At +the base of this are two bands of dark clay. These bands +become filled with water, and flow out, causing the sandrock +which rests on them to break away in large masses, +and fall on to the beach.</p> + +<p>It is clay bands such as these which are the cause of +our Undercliffs in the Isle of Wight. Turn the point, +and you see exactly how an undercliff is formed. You +see a wide platform at the level of the clay, which has +slipped out, and let down the sandrock which rested on it. +Beyond Luccombe Chine a large landslip took place in +1910, a great mass of cliff breaking away, and leaving a +<span class='pagenum'><a name="Page_26" id="Page_26">[Pg 26]</a></span> +ravine behind partly filled with fallen pine trees. The +whole fallen mass has since sunk lower and nearer to the +sea. The broken ground overgrown with trees called the +Landslip, as well as the whole extent of the ground from +Ventnor and Niton, has been formed in a similar way. +But the clay which by its slip has produced these is +another clay called the Gault, higher up in the strata. +At the top of the high cliff near Luccombe Chine a hard +gritty stratum of rock called the Carstone is seen above +the Sandrock, and above it lies the Gault clay, which +flows over the edge of the cliff.</p> + +<p>In the rock ledges and fallen blocks of stone between +Shanklin and Luccombe many more fossils may be found +than in the lower part of the Ferruginous sands. Besides +bands of oysters, blocks of stone are to be found crowded +with a pretty little shell called <i>Rhynchonella</i>. There are +others with many <i>Terebratulæ</i>, and others with fragments +of sea urchins. The Terebratulæ and Rhynchonellæ +belong to a curious group of shells, the Brachiopods, which +are placed in a class distinct from the Mollusca proper. +They were very common in the very ancient seas of the +Cambrian period,—the period of the most ancient fossils +yet found,—and some, the Lingulæ, have lived on almost +unchanged to the present day. One of the two valves is +larger than the other, and near the smaller end you will +see a little round hole. Out of this hole, when the creature +was alive, came a sort of neck, which attached it to the +rock, like the barnacles. There is a very hard ferruginous +band, of which nodules may be found along the shore, +full of beautifully perfect impressions of fossils, though +the fossils themselves are gone. Casts of a little round +bivalve shell, <i>Thetironia minor</i>, may easily be got out. +The nodules also contain casts of Trigonia, Panopœa, etc. +A stratum is sometimes exposed on the shore containing +fossils converted into pyrites. A long shell, <i>Gervillia +sublanceolata</i>, is the most frequent.</p> + +<p><span class='pagenum'><a name="Page_27" id="Page_27">[Pg 27]</a></span> +All the shells we have found are of sea creatures, and +show us that the Greensand was a marine formation. +But the strata were formed in shallow water not far from +the shore. We have learnt that coarse sediment like sand +is not carried by the sea far from the coast. And a good +deal of the Greensand is coarser than sand. There are +numerous bands of small pebbles. The pebbles are of +various kinds; some are clear transparent quartz, bits of +rock-crystal more or less rounded by rolling on the shore +of the Greensand period. These go by the name of Isle +of Wight diamonds, and are very pretty when polished. +Another mark of the nearness of the shore when these +beds were laid down is the current bedding, of which a +good example may be seen in the cliff at the north of +Shanklin parade. It is sometimes called false bedding, +for the sloping bands do not mark strata laid down +horizontally at the bottom of the sea, but a current has +laid down layers in a sloping way,—it may be just over +the edge of a sandbank. Again notice how much wood is +to be seen in the strata. Land was evidently not far off. +All along the shore you may find hard pieces of mineralised +wood, the rings of growth often showing clearly. Frequently +marine worms have bored into them before they +were locked up in the strata; the holes being generally +filled afterwards with stone or pyrites.</p> + +<p>The wood is mostly portions of trunks or branches of +coniferous trees. We also find stems of cycads. There +has been found at Luccombe a very remarkable fruit of +a kind of cycad. We said that in the Wealden period +none of our flowering plants grew. But these specimens +found at Luccombe show that cycads at that time were +developing into flowering plants. Wonderful specimens +of what may almost be called cycad flowers have been +found in strata of about this age in Wyoming in America; +and this Luccombe cycad,—called Benettites Gibsonianus,—shows +what these were like in fruit. Remains of +<span class='pagenum'><a name="Page_28" id="Page_28">[Pg 28]</a></span> +various cycadeous plants have been found in the corresponding +strata at Atherfield; and possibly by further +research fresh knowledge may be gained of an intensely +interesting story,—the history of the development of +flowering plants.</p> + +<p>On the whole the vegetation of the period was much +the same as in the Wealden. But these flowering cycads +must have formed a marked addition to the landscape,—if +indeed they did not already exist in the Wealden times. +The cones of present day cycads are very splendidly +coloured,—orange and crimson,—and it can hardly be +doubted that the cycad flowers were of brilliant hues.</p> + +<p>The land animals were still like the Wealden reptiles. +Bones of large reptiles may at times be found on the +shore at Shanklin. Several have been picked up recently. +From the prevalence of cycads we may conclude that the +climate of the Wealden and Lower Greensand was sub-tropical. +The existing Cycadaceæ are plants of South +Eastern Asia, and Australia, the Cape, and Central +America. The forest of trees allied to pines and firs and +cedars probably occupied the higher land. Turtles and +the corals point to warm waters. The existing species of +Trigonia are Australian shells. This beautiful shell is +found plentifully in Sydney harbour. It possesses a +peculiar interest, as the genus was supposed to be extinct, +and was originally described from the fossil forms, and +was afterwards found to be still living in Australia.</p> + +<div class="footnote"><p><a name="Footnote_A_3" id="Footnote_A_3"></a><a href="#FNanchor_A_3"><span class="label">[3]</span></a> Carbonate of lime has been replaced by carbonate of iron, and +the latter converted into peroxide of iron. At Sandown oxidation +has gone through the whole cliff.</p></div> +<p> </p> +<p> </p> + +<a name="Fig_2" id="Fig_2"></a> +<div class="text_rt smcap">Fig. 2</div> + +<div class="center"> + <div style="width:594px;" class="figcenter"> + <img src="images/fig_2.png" width="594" height="127" title="Coast Atherfield To Rocken End" alt="Coast Atherfield To Rocken End" /> + </div> + <table class="smaller" summary="Strata List"> + <tr><td colspan=9 class="center">COAST ATHERFIELD TO ROCKEN END</td></tr> + <tr><td colspan=9> </td></tr> + <tr><td> </td><td>Wl</td><td><i>Wealden Beds.</i></td><td> </td><td>W</td><td><i>Walpen Clay.</i></td><td> </td><td>Fer</td><td><i>Ferruginous Bands of Blackgang Chine.</i></td></tr> + <tr><td> </td><td>P</td><td><i>Perna Bed.</i></td><td> </td><td>Uc</td><td><i>Upper Crioceras Beds.</i></td><td> </td><td>B</td><td><i>Black Clay.</i></td></tr> + <tr><td> </td><td>A</td><td><i>Atherfield Clay.</i></td><td> </td><td>WS</td><td><i>Walpen and Ladder Sands.</i></td><td> </td><td>S</td><td><i>Sandrock and Clays.</i></td></tr> + <tr><td> </td><td>Ck</td><td><i>Cracker Group.</i></td><td> </td><td>Ug</td><td><i>Upper Gryphæa Beds.</i></td><td> </td><td> </td><td> </td></tr> + <tr><td> </td><td>Lg</td><td><i>Lower Gryphæa Beds.</i></td><td> </td><td>Ce</td><td><i>Cliff End Sands.</i></td><td> </td><td> </td><td> </td></tr> + <tr><td> </td><td>Sc</td><td><i>Scaphite. "</i></td><td> </td><td>F</td><td><i>Foliated Clay.</i></td><td> </td><td> </td><td> </td></tr> + <tr><td> </td><td>Lc</td><td><i>Lower Crioceras "</i></td><td> </td><td>SU</td><td><i>Sands of Walpen Undercliff.</i></td><td> </td><td> </td><td> </td></tr> + </table> +</div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_29" id="Page_29">[Pg 29]</a></span></p> + +<div class="chapt_hdr">Chapter V</div> + +<div class="chapt_ttl">BROOK AND ATHERFIELD</div> + + +<p>To most Sandown Bay is by far the most accessible place +in the Island to study the earlier strata; and for our +first geological studies it has the advantage of showing a +succession of strata so tilted that we can pass over one +formation after another in the course of a short walk. +But when we have learnt the nature of geological research, +and how to read the record of the rocks, and examined +the Wealden and Greensand strata in Sandown Bay, we +shall do well, if possible, to make expeditions to Brook +and Atherfield, to see the splendid succession of Wealden +and Greensand strata shown in the cliffs of the south-west +of the Island. It is a lonely stretch of coast, wild and +storm-swept in winter. But this part of the Island is +full of interest and charm to the lover of Nature and of +the old-world villages and the old churches and manor +houses which fit so well into their natural surroundings. +The villages in general lie back under the shelter of the +downs some distance from the shore; a coastguard station, +a lonely farm house, or some fishermen's houses as at +Brook, forming the only habitations of man we come to +along many miles of shore. Brook Point is a spot of great +interest to the geologist. Here we come upon Wealden +strata somewhat older than any in Sandown Bay. The +shore at the Point at low tide is seen to be strewn with +the trunks of fossil trees. They are of good size, some +20 ft. in length, and from one to three feet in diameter. +They are known as the Pine Raft, and evidently form a +mass of timber floated down an ancient river, and stranded +<span class='pagenum'><a name="Page_30" id="Page_30">[Pg 30]</a></span> +near the mouth, just as happens with great accumulations +of timber which float down the Mississippi at the present +day. The greater part of the wood has been replaced +by stone, the bark remaining as a carbonaceous substance +like coal, which, however, is quickly destroyed when +exposed to the action of the waves. The fossil trees are +mostly covered with seaweed. On the trunks may sometimes +be found black shining scales of a fossil fish, +<i>Lepidotus Mantelli</i>. (A stratum full of the scales of +<i>Lepidotus</i> has been recently exposed in the Wealden of +Sandown Bay.) The strata with the Pine Raft form the +lowest visible part of the anticline. From Brook Point +the Wealden strata dip in each direction, east and west. +As the coast does not cut nearly so straight across the +strata as in Sandown Bay, we see a much longer section +of the beds. On either side of the Point are coloured +marls, followed by blue shales, as at Sandown. To the +westward, however, after the shales we suddenly come to +variegated marls again, followed by a second set of shales. +There was long a question whether this repetition is due +to a fault, or whether local conditions have caused a +variation in the type of the beds. The conclusion of the +Geological Survey Memoir, 1889, rather favoured the +latter view, on the ground of the great change which has +taken place in the character of the beds in so short a +distance, assuming them to be the same strata repeated. +The conjecture of the existence of a fault has, however, +been confirmed; for during the last years a most interesting +section has been visible at the junction of the shales +and marls, where a fault was suspected. The shales in +the cliff and on the shore are contorted into the form of a +<span class="bold bigger">Z</span>. The section appears to have become visible about +1904 (it was in the spring of that year that I first saw it), +and was described by Mr. R. W. Hooley, F.G.S. (<i>Proc. +Geol. Ass.</i>, vol. xix., 1906, pp. 264, 265). It has remained +visible since.</p> + +<p><span class='pagenum'><a name="Page_31" id="Page_31">[Pg 31]</a></span> +The Wealden of Brook and the neighbouring coast is +celebrated for the number of bones of great reptiles found +here, from the early days of geological research, the '20's +and '30's of last century, when admirable early geologists, +such as Dr. Buckland and Dr. Mantell, were discovering +the wonders of that ancient world, to the present time. +Various reptiles have been found besides the Iguanodon—the +Megalosaurus, a great reptile somewhat similar, but +of lighter build, with sabre-shaped teeth, with serrated +edges: the Hylæosaurus, a smaller creature with an +armour of plates on the back, and a row of angular spines +along the middle of the back; the huge <i>Hoplosaurus +hulkei</i>, probably 70 or 80 feet in length; the marine +Plesiosaurus and Ichthyosaurus, and several more; also +bones of a freshwater turtle and four types of crocodiles. +In various beds a large freshwater shell, <i>Unio valdensis</i>, +occurs, and in the cliffs of Brook have been found many +cones of Cycadean plants. In bands of white sandy clay +are fragments of ferns, <i>Lonchopteris Mantelli</i>. In the +shales are bands of limestone with Cyrena, Paludina, and +small oysters, and paper shales with cyprids, as at Sandown. +The shore near Atherfield Point is covered with +fallen blocks of the limestones.</p> + +<p>The Lower Greensand is seen in Compton Bay on the +northern side of the Brook anticline. Here is a great +slip of Atherfield clay. The beds above the clay are +much thinner than at Atherfield, and fossils are comparatively +scarce. On the south of the anticline the +Perna bed slopes down to the sea about 150 yards east of +Atherfield Point, and runs out to sea as a reef. Large +blocks lie on the shore, where numerous fossils may be +found on the weathered surfaces. The ledges which here +run out to sea form a dangerous reef, on which many +vessels have struck. There is now a bell buoy on the reef. +On the headland is a coastguard station, and till lately +there has been a sloping wooden way from the top of the +<span class='pagenum'><a name="Page_32" id="Page_32">[Pg 32]</a></span> +cliff to bring the lifeboat down. This was washed away +in the storms of the winter 1912-13.</p> + +<p>Above the Perna bed lies a great thickness of Atherfield +clay. Above this lies what is called the Lower Lobster +bed, a brown clay and sand, in which are numerous nodules +containing the small lobster <i>Meyeria vectensis</i>,—known as +Atherfield lobsters. Many beautiful specimens have been +obtained.</p> + +<p>We next come to a great thickness of the Ferruginous +Sands, some 500 feet. The Lower Greensand of Atherfield +was exhaustively studied in the earlier days of geology +by Dr. Fitton, in the years 1824-47, and the different +strata are still referred to according to his divisions. The +lowest bed is the Crackers group about 60 ft. thick. In +the lower part are two layers of hard calcareous boulder-shaped +concretions, some a few feet long. The lower +abound in fossils, and though hard when falling from the +cliffs are broken up by winter frosts, showing the fossils +they contain beautifully preserved in the softer sandy +cores of the concretions. <i>Gervillia sublanceolata</i> is very +frequent, also <i>Thetironia minor</i>, the Ammonite <i>Hoplites +deshayesi</i>, and many more. Beneath and between the +nodular masses caverns are formed, the resounding of the +waves in which has given the name of the "Crackers." +In the upper part of this group is a second lobster bed.</p> + +<p>The most remarkable fossils in the Lower Greensand +are the various genera and species of the ammonites and +their kindred. The Ammonite, through many formations, +was one of the largest, and often most beautiful shells. +There were also quite small species. The number of +species was very great. Now the whole group is extinct. +They most resembled the Pearly Nautilus, which still lives. +In both the shell is spiral, and consists of several chambers, +the animal living in the outer chamber, the rest being +air-chambers enabling it to float. The class Cephalopoda, +which includes the Ammonites, the Nautilus, and also the +<span class='pagenum'><a name="Page_33" id="Page_33">[Pg 33]</a></span> +Cuttle-fish, is the highest division of the Mollusca. The +animals all possess heads with eyes, and tentacles around +the mouth. They nearly all possess a shell, either external, +as in the Nautilus, or internal, as in the cuttle-fishes, the +internal shell of which is often washed ashore after a +rough sea. The Cephalopods are divided into two orders. +The first includes the Cuttle-fish and the Argonaut or +Paper Nautilus. Their tentacles are armed with suckers, +and they have highly-developed eyes. They secrete an +inky fluid, which forms sepia. The internal shell of +extinct species of cuttle-fish, of a cylindrical shape, with +a pointed end, is a common fossil in various strata, and +is known as a Belemnite (Gr. <a name="Greek_belemnon">βελεμων</a> "a dart".) +The second order includes the Pearly Nautilus of the present +day, and the numerous extinct Nautiloids and Ammonoids. +The tentacles of the Pearly Nautilus have no suckers; +and the eyes are of a curiously primitive structure,—what +may be called a pin-hole camera, with no lens. The +shells of the Nautilus and its allies are of simpler form, +while the Ammonites are characterised by the complicated +margins of the partition walls or septa, by which the +shells are sub-divided. The chambers of the fossil +Ammonites have often been filled with crystals of rich +colours; and a polished section showing the chambers +is then a most beautiful object.<a name="FNanchor_A_4" id="FNanchor_A_4"></a><a href="#Footnote_A_4" class="fnanchor">[4]</a></p> + +<p>Continuing along the shore, we come to the Lower +Exogyra group, where <a href="#Terebratula"><i>Terebratula sella</i></a> is found in great +abundance. A reef with <i>Exogyra sinuata</i> runs out about +350 yards west of Whale Chine. The group is 33 ft. thick, +and is followed by the Scaphites group, 50 ft. The beds +contain <i>Exogyra sinuata</i>, and a reef with clusters of +Serpulæ runs out from the cliff. In the middle of the +group are bands of nodules containing <i>Macroscaphites +gigas</i>. The Lower Crioceras bed (16 ft.) follows, and +<span class='pagenum'><a name="Page_34" id="Page_34">[Pg 34]</a></span> +crosses the bottom of Whale Chine. The Scaphites and +Crioceras are Cephalopoda, related to the Ammonites; +but in this Lower Cretaceous period a remarkable development +took place; many of the shells began to take +curious forms, to unwind as it were. Crioceras, a very +beautiful shell, has the form of an Ammonite, but the +whorls are not in contact; thus making an open spiral +like a ram's horn, whence its name (Gk. <a name="Greek_keras">κέρος</a>, ram, +<a name="Greek_krios">κριός</a>, horn). Ancyloceras begins like Crioceras, but from +the last whorl continues for some length in a straight course, +then bends back again; Macroscaphites is similar, but the +whorls of the spiral part are in contact. In Scaphites, a +much smaller shell, the uncoiled part is much shorter, +and its outline more rounded. It is named from its +resemblance to a boat (Gk. <a name="Greek_skaphe">σκάφη</a>).<a name="FNanchor_A_5" id="FNanchor_A_5"></a><a href="#Footnote_A_5" class="fnanchor">[5]</a></p> + +<p>The Walpen and Ladder Clays and Sands (about 60 ft.) +contain nodules with Exogyra and the Ammonite +<i>Douvilleiceras martini</i>. The dark-green clays of the lower +part form an undercliff, on to which Ladder Chine opens. +The Upper Crioceras Group (46 ft.), like the Lower, contains +bands of Crioceras? also <i>Douvilleiceras martini</i>, +Gervillia, Trigonia, etc. It must be stated that there +is some uncertainty with regard to the ammonoids found +in this neighbourhood, Macroscaphites having been +described as Ancyloceras, and also sometimes as Crioceras. +The discovery of the true Ancyloceras (<i>Ancyloceras +Matheronianum</i>) at Atherfield is described (and a figure +given) by Dr. Mantell; but what is the characteristic +ammonoid of the "Crioceras" beds requires further +investigation. The neighbourhood of Whale and Walpen +Chines is of great interest. Ammonites may be found in +the bottom of Whale Chine fallen out of the rock. Red +ferruginous nodules with Ammonites lie on the shore, +in the Chines, and on the Undercliff, some of the ammonites +more or less converted into crystalline spar. +<span class='pagenum'><a name="Page_35" id="Page_35">[Pg 35]</a></span> +Hard ledges of the Crioceras beds run into the sea. The +shore is usually covered deep with sand and small shingle; +but there are times when the sea has washed the ledges +clear; and it is then that the shore should be examined.</p> + +<p>The Walpen and Ladder Sands (42 ft.); the Upper +Exogyra Group (16 ft.); the Cliff End Sand (28 ft.); and +the Foliated Clay and Sand (25 ft.), consisting of thin +alternations of greenish sand and dark-blue clay, follow. +Then the Sands of Walpen Undercliff (about 100 ft.); +over which lie the Ferruginous Bands of Blackgang Chine +(20 ft.). Over these hard beds the cascade of the Chine +falls. Cycads and other vegetable remains are found in +this neighbourhood. Throughout the Atherfield Greensand +fragments of the fern <i>Lonchopteris</i> (<i>Weichselia</i>) +<i>Mantelli</i> are found. 220 ft. of dark clays and soft white +or yellow sandrock complete the Lower Greensand. In +the upper beds of the Greensand few organic remains +occur. A beautiful section of Sandrock with the junction +of the Carstone is to be seen inland at Rock above Bright-stone. +The Sandrock here is brightly coloured like the +sands of Alum Bay,—though it belongs to a much older +formation,—and shows current bedding very beautifully. +The junction of the Sandrock and Carstone is also well +seen in the sandpit at Marvel.</p> + +<p>We have now come to the end of the Lower Cretaceous, +in which are included the Wealden and the Lower Greensand. +Judged by the character of the flora and fauna, +the two form one period, the main difference being the +effect of the recession of the shore line, due to the subsidence +which let in the sea over the Wealden delta, so +that we have marine strata in place of freshwater deposits. +But that the plants and animals of the Wealden age still +lived in the not distant continent is shown by the remains +borne down from the land. These strata are an example +of a phenomenon often met with in geology,—that of a +great thickness of deposits all laid down in shallow water.<span class='pagenum'><a name="Page_36" id="Page_36">[Pg 36]</a></span> +The Wealden of the Isle of Wight are some 700 feet thick, +in Kent a good deal thicker, the Hastings Sands, the +lower part of the formation, being below the horizon +occurring in the Island: the Lower Greensand is some +800 feet thick. In the ancient rocks of Wales, the +Cambrian and Silurian strata, are thousands of feet of +deposits, mostly laid down in fairly shallow water. In +such cases there has been a long-continued deposition of +sediment, while a subsidence of the area in which it was +laid down has almost exactly kept pace with the deposit. +It is difficult not to conclude that the subsidence has been +caused by the weight of the accumulating deposit,—continuing +until some world-movement of the contracting +globe has produced a compensating elevation of the area.</p> + +<div class="footnote"><p><a name="Footnote_A_4" id="Footnote_A_4"></a><a href="#FNanchor_A_4"><span class="label">[4]</span></a> Some fine ammonites may be seen at the Clarendon Hotel, +Chale,—one about 5 ft. in circumference.</p></div> + +<div class="footnote"><p><a name="Footnote_A_5" id="Footnote_A_5"></a><a href="#FNanchor_A_5"><span class="label">[5]</span></a> <i>See Guide to Fossil Invertebrata</i>, Brit. Mus. Nat. Hist.</p></div> + +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_37" id="Page_37">[Pg 37]</a></span></p> + +<div class="chapt_hdr">Chapter VI</div> + +<div class="chapt_ttl">THE GAULT AND UPPER GREENSAND</div> + + +<p>We have seen how the continent through which the great +Wealden river flowed began to sink below the sea level, +and how the waters of the sea flowed over what had been +the delta of the river, laying down the beds of sandstone +with some mixture of clay which we call the Lower +Greensand. The next stratum we come to is a bed of +dark blue clay more or less sandy, called the Gault. In +the upper beds it becomes more sandy and grey in colour. +These are known as the "passage beds," passing into the +Upper Greensand. The thickness of the Gault clay +proper varies from some 95 to 103 feet. Compared to the +mainland the Gault is of small thickness in the Island, +though the dark clay bands in the Sandrock mark the +oncoming of similar conditions. The fine sediment +forming the clay points to a further sinking of the sea +bed. In general, we find very few fossils in the Gault +in the Island, though it is very fossiliferous on the +mainland at Folkestone. North of Sandown Red Cliff +the Gault forms a gully, down which a footpath leads +to the shore. It is seen at the west of the Island in +Compton Bay, where in the lower part some fossil shells +may be found.</p> + +<p>The Upper Greensand is not very well named, as the +beds only partially consist of sandstone, in great part of +quite other materials. Some prefer to call the Lower +Greensand Vectian, from Vectis, the old name of the Isle +of Wight, and the Upper Greensand Selbornian, a name +generally adopted, because it forms a marked feature of +<span class='pagenum'><a name="Page_38" id="Page_38">[Pg 38]</a></span> +the country about Selborne in Hampshire.<a name="FNanchor_A_6" id="FNanchor_A_6"></a><a href="#Footnote_A_6" class="fnanchor">[6]</a> But, +though the Upper Greensand covers a less area in the +Isle of Wight than the Lower, it forms some of the most +characteristic scenery of the Island. One of the most +striking features of the Island is the Undercliff, the +undulating wooded country from Bonchurch to Niton, +above the sea cliff, but under a second cliff, a vertical +wall which shelters it to the North. This wall of cliff +consists of Upper Greensand. In a similar way to the +small undercliffs we saw at Luccombe, the Undercliff has +been formed by a series of great slips, caused here by the +flowing out of the Gault clay, which runs in a nearly +horizontal band through the base of all the Southern +Downs of the Island, the Upper Greensand lying above +it breaking off in masses, and leaving vertical walls of +cliff. These walls are seen not only in the Undercliff, but +also on the northern side of the downs, where they form +the inland cliff overhanging a pretty belt of woodland +from Shanklin to Cook's Castle, and again forming Gat +Cliff above Appuldurcombe. We have records of great +landslips at the two ends of the Undercliff, near Bonchurch +and at Rocken End, about a century ago. But +the greater part of the Undercliff was formed by landslips +in very ancient times, before recorded history in this +Island began. The outcrop of the Gault is marked by a +line of springs on all sides of the Southern Downs. The +strata above, Chalk and Upper Greensand, are porous +and absorb the rainfall, which permeates through till it +reaches the Gault Clay, which throws it out of the hill +side in springs, some of which furnish a water supply for +the surrounding towns and villages.</p> + +<p><span class='pagenum'><a name="Page_39" id="Page_39">[Pg 39]</a></span> +Where the Upper Greensand is best developed, above +the Undercliff, the passage beds are followed by 30 feet +of yellow micaceous sands, with layers of nodules of a +bluish-grey siliceous limestone known as Rag. The +nodules frequently contain large Ammonites and other +fossils. Next follow the Sandstone and Rag beds, about +50 feet of sandstone with alternating layers of rag. The +sandstones are grey in colour, weathering buff or reddish-brown, +tinged more or less green by grains of glauconite. +Near the top of these strata is the Freestone bed, a thick +bed of a close-grained sandstone, weathering a yellowish +grey, which forms a good building stone. Most of the +churches and old manor and farm houses in the southern +half of the Island are built of this stone. Then forming +the top of the series are 24 feet of chert beds,—bands of +a hard flinty rock called chert alternating with siliceous +sandstone, the sandstone containing large concretions of +rag in the same line of bedding. The chert beds are very +hard, and where the strata are horizontal, as above the +Undercliff, project like a cornice at the top of the cliff. +Perhaps the finest piece of the Upper Greensand is Gore +Cliff above Niton lighthouse, a great vertical wall with +the cornice of dark chert strata overhanging at the top. +The thickness in the Undercliff, including the Passage +Beds, is from 130 to 160 ft.</p> + +<p>The Upper Greensand may be studied at Compton Bay, +and at the Culvers; and along the shore west of Ventnor +the lower cliff by the sea consists largely of masses of +fallen Upper Greensand, many of which show the chert +strata well. In numerous walls in the south of the Island +may be seen stone from the various strata—sandstone, +blue limestone or rag, and also the chert.</p> + +<p>Let us think what was happening when these beds were +being formed. The sandstone is much finer than that +of the Lower Greensand; and we have limestones now,—marine, +not freshwater as in the Wealden. Marine limestones +are formed by remains of sea creatures living at +some depth in clear water. And now we come to a new +material, chert. It is not unlike flint, and flint is one of +the mineral forms of silica. Chert may be called an +<span class='pagenum'><a name="Page_40" id="Page_40">[Pg 40]</a></span> +impure or sandy flint. The bands of chert appear to have +been formed by an infiltration of silica into a sandstone, +forming a dense flinty rock, which, however, has a dull +appearance from the admixture of sand, instead of being +a black semi-transparent substance like flint. But where +did the silica come from? In the depths of the sea many +sea creatures have skeletons and shells formed of silica +or flint, instead of carbonate of lime, which is the material +of ordinary shells and of corals. Many sponges, instead +of the horny skeleton we use in the washing sponge, have +a skeleton formed of a network of needles of silica, often +of beautiful forms. Some marine animalcules, the +Radiolaria, have skeletons of silica. And minute plants, +the Diatoms, have coverings of silica, which remain like +a little transparent box, when the tiny plant is dead. +Now, much of the chert is full of needles, or spicules, as +they are called, of sponges, and this points to the source +from which some at least of the silica was derived. To +form the chert much of the silica has been in some manner +dissolved, and deposited again in the interstices of sandstone +strata. We shall have more to say of this process +when we come to speak of the origin of the flints in the +chalk. Sponges usually live in clear water of some depth; +so all shows that the sea was becoming deeper when these +strata were being formed.</p> + +<p>Along the shore of the Undercliff, Upper Greensand +fossils may be found nicely weathered out. Very common +is a small curved bivalve shell,—a kind of small oyster,—<i>Exogyra +conica</i>, as are also serpulæ, the tubes formed by +certain marine worms. Very pretty pectens (scallop +shells) are found in the sandstone. Many other shells, +<i>Terebratulæ</i>, <i>Trigonia</i>, <i>Panopæa</i>, etc., occur, and several +species of ammonite and nautilus.<a name="FNanchor_A_7" id="FNanchor_A_7"></a><a href="#Footnote_A_7" class="fnanchor">[7]</a> A frequent fossil is +a kind of sponge, Siphonia. It has the form of an oblong +bulb, supported by a long stem, with a root-like base. +It is often silicified, and when broken shows bundles of +tubular channels.</p> + +<p><span class='pagenum'><a name="Page_41" id="Page_41">[Pg 41]</a></span> +In the chert may often be seen pieces of white or bluish +chalcedony, generally in thin plates filling cracks in the +chert. This is a very pure and hard form of silica, +beautifully clear and translucent. Pebbles which the +waves have worn in the direction of the plate are very +pretty when polished, and go by the name of sand agates. +They may sometimes be picked up on the shore near the +Culvers.</p> + +<div class="footnote"><p><a name="Footnote_A_6" id="Footnote_A_6"></a><a href="#FNanchor_A_6"><span class="label">[6]</span></a> Names proposed by the late A. J. Jukes-Browne.</p></div> + +<div class="footnote"><p><a name="Footnote_A_7" id="Footnote_A_7"></a><a href="#FNanchor_A_7"><span class="label">[7]</span></a> Of Ammonites, <i>Mortoniceras rostratum</i> and <i>Hoplites splendens</i> +may be mentioned: and of Pectens, <i>Neithea quinquecostata</i> and +<i>quadricostata</i>, <i>Syncyclonema orbicularis</i>, and <i>Æquipecten asper</i>.</p></div> + +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_42" id="Page_42">[Pg 42]</a></span></p> + +<div class="chapt_hdr">Chapter VII</div> + +<div class="chapt_ttl">THE CHALK</div> + +<p>As we have traced the world's history written in the +rocks we have seen an old continent gradually submerged, +a deepening sea flowing over this part of the earth's +surface. Now we shall find evidence of the deepening of +the sea to something like an ocean depth. We are coming +to the great period of the Chalk, the time when the material +was made which forms the undulating downs of the south east +of England, and of which the line of white cliffs +consists, which with sundry breaks half encircles our +shores, from Flamborough Head in Yorkshire, by Dover +and the Isle of Wight, to Bere in Devon. Across the +Channel white cliffs of chalk face those of England, and +the chalk stretches inland into the Continent. Its extent +was formerly greater still. Fragments of chalk and flint +are preserved in Mull under basalt, an old lava flow, and +flints from the chalk are found in more recent deposits +(Boulder Clay) on the East of Scotland, pointing to a +former great extension northward, which has been nearly +all removed by denudation. In the Isle of Wight the +chalk cliffs of Freshwater and the Culvers are the grandest +features of the Island; while all the Island is dominated +by the long lines of chalk downs running through it from +east to west. Now what is the chalk? And how was it +made? The microscope must tell us. It is found that +this great mass of chalk is made up principally of tiny +microscopic shells called Foraminifera, whole and in crushed +fragments. There are plenty of foraminifera in the seas +to-day; and we need not go far to find similar shells. +<span class='pagenum'><a name="Page_43" id="Page_43">[Pg 43]</a></span> +On the shore near Shanklin you will often see streaks of +what look like tiny bits of broken shell washed into +depressions in the sand. These, however, often consist +almost entirely of complete microscopic shells, some of +them of great beauty. The creature that lives in one +of these shells is only like a drop of formless jelly, and yet +around itself it forms a complex shell of surprising beauty. +The shells are pierced with a number of holes, hence their +name (fr. Lat. <i>foramen</i>, a hole, and <i>ferre</i>, to bear). +Through these holes the animal puts out a number of +feelers like threads of jelly, and in these entangles particles +of food, and draws them into itself. Now, do we anywhere +to-day find these tiny shells in such masses as to build +up rocks? We do. The sounding apparatus, with which +we measure the depths of the sea, is so constructed as to +bring up a specimen of the sea bottom. This has been +used in the Atlantic, and it is found that the really deep +sea bottom, too far out for rivers and currents to bring +sand and mud from the land, is covered with a white mud +or ooze. And the microscope shows this to be made up +of an unnumerable multitude of the tiny shells of foraminifera. +As the little creatures die in the sea, their shells +accumulate on the bottom, and in time will be pressed +into a hard mass like chalk, the whole being cemented +together by carbonate of lime, in the way we explained +in describing the making of limestones. So we find chalk +still forming at the present day. But what ages it must +take to form strata of solid rock of such tiny shells! And +what a vast period of time it must have required to build +up our chalk cliffs and downs, composed in large part of +tiny microscopic shells! With the foraminifera the +microscope shows in the chalk a multitude of crushed +fragments, largely the prisms which compose bivalve +shells, flakes of shells of Terebratula and Rhynchonella, +and minute fragments of corals and Bryozoa. Scattered +in the chalk we shall also find larger shells and other +<span class='pagenum'><a name="Page_44" id="Page_44">[Pg 44]</a></span> +remains of the life of the ancient sea. The base of the +cliffs and fallen blocks on the shore are the best places to +find fossils. Much of the base of the cliffs is inaccessible +except by boat. The lower strata may be examined in +Sandown and Compton Bays, and the upper in Whitecliff +Bay. A watch should always be kept on the tide. +The quarries along the downs are not as a rule good for +collecting, as the chalk does not become so much sculptured +by weathering.</p> + +<p>The deep sea of the White Chalk did not come suddenly. +In the oncoming of the period we find much marl—limy +clay. As the sea deepened, little reached the bottom but +the shells of foraminifera and other marine organisms. +How deep the sea became is uncertain: there is reason to +believe that it did not reach a depth such as that of the +Atlantic.</p> + +<p>It is difficult to draw the line between the Upper +Greensand and the Chalk strata. Above the Chert beds +is a band a few feet thick known as the Chloritic Marl, +which shows a passage from sand to calcareous matter. +It is named from the abundance of grains of green colouring +matter, now recognised as glauconite; so that it +would be better called Glauconitic Marl. It is also remarkable +for the phosphatic nodules, and for the numerous +casts of Ammonites, Turrilites, and other fossils mostly +phosphatized, which it contains. This band is one of +the richest strata in the Island for fossils. It differs, +however, in different localities both in thickness and +composition. It is best seen above the Undercliff, and +in fallen masses along the shore from Ventnor to Niton. +It is finely exposed on the top of Gore Cliff, where the flat +ledges are covered with fossil Ammonites, Turrilites, +Pleurotomaria, and other shells. The Ammonite (<i>Schloenbachia +varians</i>) is especially common. The sponge +(<i>Stauronema carteri</i>) is characteristic of the Glauconitic +Marl. As the edge of the cliff is a vertical wall, none +should try this locality but those who can be trusted to +take proper care on the top of a precipice. When a high +wind is blowing the position may be especially dangerous.</p> +<p> </p> +<p> </p> + +<a name="Plate_III" id="Plate_III"></a> +<div class="smcap text_rt">PL. III</div> + + <table width="100%" class="center" summary="Plate III"> + <tr><td><img src="images/pl_iii_pecten.png" width="86" height="102" title="Pecten" alt="Pecten" /><br /><span class="smaller smcap">(Pecten)</span></td> + <td><img src="images/pl_iii_neithea.png" width="155" height="109" title="Neithea Quinquecostata" alt="Neithea Quinquecostata" /><br /><span class="smaller smcap">Neithea Quinquecostata</span></td></tr> + + <tr><td colspan=2><img src="images/cleardot.png" width="2" height="32" title=" " alt=" " /></td></tr> + + <tr><td colspan=2> + <table width="100%" summary="Plate III cont."> + <tr><td><img src="images/pl_iii_thetironia.png" width="84" height="65" title="Thetironia Minor" alt="Thetironia Minor" /><br /><span class="smaller smcap">Thetironia Minor</span></td><td class="center"><img src="images/pl_iii_mantelliceras.png" width="178" height="143" title="Mantelliceras Mantelli" alt="Ammonite" /><br /><span class="smaller smcap">(Ammonite)<br />Mantelliceras Mantelli</span></td><td><img src="images/pl_iii_rhynchonella.png" width="74" height="72" title="Rhynchonella Parvirostris" alt="Rhynchonella Parvirostris" /><br /><span class="smaller smcap">Rhynchonella<br>Parvirostris</span></td></tr> + </table> + </td></tr> + + <tr><td colspan=2><img src="images/cleardot.png" width="2" height="32" title=" " alt=" " /></td></tr> + + <tr><td><img src="images/pl_iii_micraster.png" width="178" height="190" title="Micraster Cor-Anguinum" alt="Micraster Cor-Anguinum" /></td><td><img src="images/pl_iii_echyinocorys.png" width="175" height="149" title="Echinocorys Scutatus" alt="Echinocorys Scutatus" /></td></tr> + <tr><td colspan=2><span class="smaller smcap">(Sea Urchins)</span></td></tr> + <tr><td><span class="smaller smcap">Micraster Cor-Anguinum</span></td><td><span class="smaller smcap">Echinocorys Scutatus</span><br /><span class="smaller">(Internal cast in flint)</span></td></tr> +</table> + +<div class="caption4">LOWER AND UPPER GREENSAND AND CHALK</div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_45" id="Page_45">[Pg 45]</a></span> +The Chloritic Marl is followed by the Chalk Marl, of +much greater thickness. This consists of alternations of +chalk with bands of Marl, and contains glauconite and +also phosphatic nodules in the lower part. Upwards it +merges into the Grey Chalk, a more massive rock, coloured +grey from admixture of clayey matter. These form the +Lower Chalk, the first of the three divisions into which +the Chalk is usually divided. Above this come the Middle +and Upper, which together form the White Chalk. They +are much purer white than the lower division, which is +creamy or grey in colour. The Chalk Marl and Grey +Chalk are well seen at the Culver Cliff, and run out in +ledges on the shore. The lower part of this division is the +most fossiliferous, and contains various species of Ammonities, +Turrilites, Nautilus, and other Cephalopoda. +(Of Ammonites <i>Schloenbachia varians</i> is characteristic. +Also may be named <i>S. Coupei</i>, <i>Mantelliceras mantelli</i>, +<i>Metacanthoplites rotomagensis</i>, <i>Calycoceras naviculare</i>, +the small Ammonoid Scaphites æqualis; and of Pectens, +<i>Æquipecten beaveri</i> and <i>Syncyclonema orbicularis</i> may be +mentioned). White meandering lines of the sponge +<i>Plocoscyphia labrosa</i> are conspicuous in the lower beds. +The Chalk Marl is well shown at Gore Cliff, sloping upwards +from the flat ledges of the Chloritic Marl. It may be +studied well, and fossils found, in the cliff on the Ventnor +side of Bonchurch Cove,—which has all slipped down +from a higher level.</p> + +<p>The uppermost strata of the Lower Chalk are known +as the Belemnite Marls. They are dark marly bands, in +which a Belemnite, <i>Actinocamax plenus</i>, is found. The +hard bands known as Melbourn Rock and Chalk Rock, +which on the mainland mark the top of the Lower and +Middle Chalk respectively, are neither of them well marked +<span class='pagenum'><a name="Page_46" id="Page_46">[Pg 46]</a></span> +in the Isle of Wight. In the Middle Chalk <i>Inoceramus +labiatus</i>, a large bivalve shell, occurs in great profusion; +and in the Upper flinty Chalk are sheets of another species, +<i>I. Cuvieri</i>. It is hardly ever found perfect, the shells +being of a fibrous structure, with the fibres at right angles +to the surface, and so very fragile.</p> + +<p>There is a striking difference between the Middle and +Upper Chalk, which all will observe. It consists in the +numerous bands of dark flints which run through the +Upper Chalk parallel to the strata. The Lower Chalk is +entirely, and the Middle Chalk nearly, devoid of flint. +Though the line at which the commencement of the Upper +Chalk is taken is rather below the first flint band of the +Upper Chalk, and a few flints occur in the highest beds +of the Middle Chalk; yet, speaking generally, the great +distinction between the Middle and Upper Chalk, the +two divisions of the White Chalk, may be considered to +be that of flintless chalk and chalk with flints.</p> + +<p>Early in our studies we noticed the great curves into +which the upheaved strata have been thrown, and that +on the northern side of the anticline the strata are in +places vertical. This can be well observed in the Culver +Cliffs and Brading Down, where the strata of the Upper +Chalk are marked by the lines of black flints. In the +large quarry on Brading Down the vertical lines of flint +can be clearly seen; and by walking at low tide at Whitecliff +Bay round the corner of the cliff, or by observing the +cliff from a boat, we may see a beautiful section of the +flinty chalk, the lines of black flints sloping at a high +angle. The flints in general form round or oval masses, +but of irregular shape with many projections, and the +masses lie in regular bands parallel to the stratification. +The tremendous earth movement which has bent the +strata into a great curve has compressed the vertical +portion into about half its original thickness, and has +made the chalk of our downs extremely hard. It has +also shattered the flints in the chalk into fragments. The +rounded masses retain their form, but when pulled out of +the chalk fall into sharp angular fragments, and we find +they are shattered through and through.</p> +<p> </p> +<p> </p> + +<a name="Photo_1" id="Photo_1"></a> +<div class="smcap text_rt">Photo 1</div> + +<div class="center"> + <div style="width: 610px" class="figcenter"> + <img src="images/ph_1_culver_cl.png" width="600" height="372" title="Culver Cliff" alt="Culver Cliff" /><br /> + <div class="photo_cap"><span class="text_lf"><i>Photo by J. Milman Brown, Shanklin.</i></span> + <span class="smcap text_rt">Culver Cliffs—Highly inclined Chalk Strata</span><br /></div> + </div> +</div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_47" id="Page_47">[Pg 47]</a></span> +Now, what are flints, and how were they formed? +Flints are a form of silica, a purer form than chert, as the +chalk in which they are embedded was formed in the deep +sea, and so we have no admixture of sand. Flints, as we +find them in the chalk, are generally black translucent +nodules, with a white coating, the result of a chemical +action which has affected the outside after they were +formed. Flint is very hard,—harder than steel. You +cannot scratch it with a knife, though you may leave a +streak of steel on the surface of the flint. This hardness +is a property of other forms of silica, as quartz and chalcedony. +The question how the flints were formed is a +difficult one. As to this much still remains obscure. +The sea contains mineral substances in solution. Calcium +sulphate and chloride, and a small amount of calcium +carbonate (carbonate of lime) are in solution in the sea. +From these salts is derived the calcium deposited as +calcium carbonate to form the shells of the Foraminifera +and the larger shells in the Chalk. There is also silica in +small quantity in sea water. From this the skeletons of +radiolaria and diatoms and the spicules of sponges are +formed. Now, many flints contain fossil sponges, and +when broken show a section of the sponge clearly marked. +Especially well can this be seen in flints which have lain +some time in a gravel bed formed of flints worn out of the +chalk by denudation. Hard as a flint seems, it is penetrated +by numerous fine pores. The gravel beds are usually stained +yellow by water containing iron, and this has penetrated by +the pores through the substance of the flints, staining them +brown and orange. Many of the stained flints show beautifully +the sponge markings,—a wide central canal with +fine thread-like canals leading into it from all sides.</p> + +<p><span class='pagenum'><a name="Page_48" id="Page_48">[Pg 48]</a></span> +The Chalk Sea evidently abounded in siliceous organisms, +and it cannot be doubted that it is from such +organisms that the silica was derived, which has formed +the masses of flint. Silica occurs in two forms—in a +crystalline form as quartz or rock crystal, and as amorphous, +<i>i.e.</i>, formless or uncrystalline (also called opaline) +silica. The siliceous skeletons of marine organisms are +formed of amorphous silica. Flint consists of innumerable +fine crystalline grains, closely packed together. +Amorphous silica is less stable than crystalline, and is +capable of being dissolved in alkaline water, <i>i.e.</i>, water +containing carbonate of sodium or potassium in solution. +If the silica so dissolved be deposited again, it is generally +in the crystalline form. It seems probable, therefore, +that the amorphous silica of the skeletal parts of marine +organisms has been dissolved by alkaline water percolating +through the strata, and re-deposited as flint.</p> + +<p>As the silica was deposited, chalk was removed. The +large irregular masses of flint lying in the Chalk strata +have clearly taken the place of chalk which has been +removed. Water charged with silica soaking through the +strata has deposited silica, and at the same time dissolved +out so much carbonate of lime. Bivalve shells, originally +carbonate of lime, are often replaced, and filled up by +flint, and casts of sea urchins in solid flint are common, +and often beautiful fossils. This process of change took +place after the foraminiferal ooze had been compacted into +chalk strata; and to some extent at any rate, there has +been deposition of silica after the chalk had become hard +and solid; for we find flat sheets, called tabular flint, +lying along the strata, or filling cracks cutting through +the strata at right angles. But in all probability the +re-arrangement of the constituents of the strata took +place in the main during the first consolidation, as the +strata rose above the sea-level, and the sea-water drained +out. A suggestion has been made by R. E. Liesegang, +<span class='pagenum'><a name="Page_49" id="Page_49">[Pg 49]</a></span> +of Dresden, to explain the occurrence of the flints in the +bands with clear interspaces between, which are such a +marked feature of the Upper Chalk. He has shown how +"a solution diffusing outward and encountering something +with which it reacts and forms a precipitate, moves on +into this medium until a concentration sufficient to cause +precipitation of the particular salt occurs. A zone of +precipitation is thus formed, through which the first +solution penetrates until the conditions are repeated, and +a second zone of precipitate is thrown down. Zone after +zone may thus arise as diffusion goes on." He suggests +that the zones of flint may be similar phenomena, water +diffusing through the masses of chalk taking up silica till +such concentration is reached that precipitation takes +place, the water then percolating further and repeating +the process.<a name="FNanchor_A_8" id="FNanchor_A_8"></a><a href="#Footnote_A_8" class="fnanchor">[8]</a></p> + +<p>The precipitation of silica and replacement of the chalk +occurs irregularly along the zone of precipitation, forming +great irregular masses of flint, which enclose the sponges +and other marine organisms that lay in the chalk strata. +Where a deposit of silica has begun, it will probably have +determined the precipitation of more silica, in the manner +constantly seen in chemical precipitation; and it would +seem that siliceous organisms as sponges have to some +extent served as centres around which silica has been +precipitated, for flints are very commonly found, having +the evident external form of sponges.</p> + +<p><span class='pagenum'><a name="Page_50" id="Page_50">[Pg 50]</a></span> +It will be well to say something here of the history of +the flints as the chalk which contains them is gradually +denuded away. Rain water containing carbonic dioxide +has a great effect in eating away all limestone rocks, chalk +included. A vast extent of chalk, which formerly covered +much of England has thus disappeared. The arch of +chalk connecting our two ranges of downs has been cut +through, and from the top of the downs themselves a +great thickness of chalk has been removed. The chalk in +the downs above Ventnor and Bonchurch is nearly +horizontal. It consists of Lower and Middle Chalk; and +probably a small bit of the Upper occurs. But the top +of St. Boniface Down is covered with a great mass of +angular flint gravel, which must have come from the +Upper Chalk. The gravel is of considerable thickness, +perhaps 20 ft., and on the spurs of the down falls over to +a lower level like a table-cloth. It is worked in many +pits for road metal. This flint gravel represents the insoluble +residue which has been left when the Chalk was +dissolved away.</p> + +<p>On the top of the cliffs between Ventnor and Bonchurch, +at a point called Highport, is a stratum of flint +gravel carried down from the top of the down. The shore +here is strewn with large flints fallen from the gravel. +The substance of many of the flints has undergone a +remarkable change. Instead of black or dull grey flint it +has become translucent agate, of splendid orange and +purple colours, or has been changed into clear translucent +chalcedony. In the agate the forms of fossil sponges can +often be beautifully seen. The colours are due to iron-charged +water percolating into the flint in the gravel bed, +but further structural changes have altered the form of +the silica; chalcedony having a structure of close crystalline +fibres, revealed by polarized light: when variously +stained and coloured, it is usually called agate. Many of +these flints, when cut through and polished, are of great +beauty. The main force of the tides along these shores +is from west to east; and so there is a continual passage +of pebbles on the shore in that direction. The flints in +Sandown Bay have in the main travelled round from +here; and towards the Culvers small handy specimens +of agates and chalcedonies rounded by the waves may +be collected.</p> +<p> </p> +<p> </p> + +<a name="Photo_2" id="Photo_2"></a> +<div class="smcap text_rt">Photo 2</div> + +<div class="center"> + <div style="width: 610px" class="figcenter"> + <img src="images/ph_2_scrathell_bay.png" width="600" height="368" title="Scratchell's Bay" alt="Scratchell's Bay" /><br /> + <div class="photo_cap"><span class="text_lf"><i>Photo by J. Milman Brown, Shanklin.</i></span> + <span class="smcap text_rt">Scratchell's Bay—Highly Inclined Chalk Strata</span><br /></div> + </div> +</div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_51" id="Page_51">[Pg 51]</a></span> +The extensive downs in the centre of the Island +are largely overspread with angular flint gravel +similarly formed to that of St. Boniface. Of other +beds of gravel, which have been washed down to a +lower level by rivers or other agency we shall have more +to say later.</p> + +<p>The Chalk strata in the Isle of Wight are of great thickness. +In the Culver Cliff there are some 400 feet of flintless +Chalk (Lower and Middle Chalk), and then some +1,000 feet of chalk with flints. There is some variation +in the thickness of the strata in different parts of the +Island, and the amount of the Upper strata, which has +been removed by denudation, varies considerably. The +average thickness of the white chalk in the Island is about +1,350 feet.<a name="FNanchor_A_9" id="FNanchor_A_9"></a><a href="#Footnote_A_9" class="fnanchor">[9]</a> Including the Lower Chalk, the maximum +thickness of the Chalk strata is 1,630 ft.</p> + +<p>The divisions of the chalk we have so far considered +depend on the character of the rock: we must say +a word about another way of dividing the strata. +It is found that in the chalk, as in other strata, +fossils change with every few feet of deposit. We may make +a zoological division of the chalk by seeing how the fossils +are distributed. The Chalk was first studied from this +point of view by the great French geologist, M. Barrois, +who divided it into zones, according to the nature of the +animal life, the zones being called by the name of some +fossil specially characteristic of a particular zone. More +recently Dr. A. W. Rowe has made a very careful study +of the zones of the White Chalk, and is now our chief +authority on the subject. The strata have been grouped +into zones as follows:—</p> + +<p><span class='pagenum'><a name="Page_52" id="Page_52">[Pg 52]</a></span></p> +<table summary="Chalk Strata Listing"> +<tr><td colspan=2> </td><td> Zones.<img src="images/cleardot.png" width="150" height="0" title="" alt=" " />Sub-Zones.</td></tr> +<tr><td rowspan=3>Upper<br />Chalk.</td><td rowspan=3><img src="images/brace_lf1.png" width="20" height="285" alt="left brace"></td><td>Belemnitella mucronata.<br />Actinocamax quadratus.</td></tr> +<tr><td> + <table summary="Upper Chalk sub unit"> + <tr><td>Offaster pilula.</td><td><img src="images/brace_lf3.png" width="18" height="69" alt="left brace"></td><td>Offaster pilula<br />Echinocorys depressus.</td></tr> + </table> + <table summary="Upper Chalk sub unit"> + <tr><td>Marsupites<br /> testudinarius.</td><td><img src="images/brace_lf3.png" width="18" height="69" alt="left brace"></td><td>Marsupites.<br />Uintacrinus.</td></tr> + </table> +</td></tr> +<tr><td>Micraster cor-anguinum.<br />Micraster cor-testudinarium.<br />Holaster planus.</td></tr> +</table> +<table summary="Middle Chalk"> +<tr><td rowspan=2>Middle<br />Chalk.</td><td rowspan=2><img src="images/brace_lf3.png" width="18" height="69" alt="left brace"></td><td>Terebratulina lata.<br />Inoceramus labiatus.</td></tr> +</table> +<table summary="Lower Chalk"> +<tr><td rowspan=2>Lower<br />Chalk.</td><td rowspan=2><img src="images/brace_lf3.png" width="18" height="69" alt="left brace"><br /><img src="images/brace_lf3.png" width="18" height="69" alt="left brace"></td><td>Holaster subglobosus<td><td><img src="images/brace_lf3.png" width="18" height="69" alt="left brace"></td><td>Actinocamax<br /> plenus (at top).</td></tr> +<tr><td>Schloenbachia varians<td><td><img src="images/brace_lf3.png" width="18" height="69" alt="left brace"></td><td>Stauronema<br /> carteri (at base).</td></tr> +</table> + +<p>The method of study according to zoological zones is +of great interest. The period of the White Chalk was of +long duration, and the physical conditions remained very +uniform. So that by studying the succession of life during +this period we may learn much about the gradual change +of life on the earth, and the evolution of living things.</p> + +<p>We have seen that the whole mass of the chalk is made +up mainly of the remains of living things,—mostly of the +microscopic foraminifera. We have seen that sponges +were very plentiful in that ancient sea. Of other fossils +we find brachiopods—different species of Terebratula and +Rhynchonella—a large bivalve <i>Inoceramus</i> sometimes +very common; the very beautiful bivalve, <i>Spondylus +spinosus</i>, belemnites, serpulæ; and different species of +sea-urchin are very common. A pretty heart-shaped one, +<i>Micraster cor-anguinum</i>, marks a zone of the higher chalk, +which runs along the top of our northern downs. Other +common sea urchins are various species of <i>Cidaris</i>, of a +form like a turban (Gk. <i>cidaris</i>, a Persian head-dress); +<i>Cyphosoma</i>, another circular form; the oval <i>Echinocorys</i> +<span class='pagenum'><a name="Page_53" id="Page_53">[Pg 53]</a></span> +<i>scutatus</i>, which, with varieties of the same and allied +species, abounds in the Upper Chalk, and the more conical +<i>Conulus conicus</i>. The topmost zone, that of <i>B. Macronata</i>, +would yield a record of exuberant life, were the +chalk soft and horizontal. There was a rich development +of echinoderms (sea urchins and star fishes), but nothing +is perfect, owing to the hardness of the rock (Dr. Rowe). +The general difference in the life of the Chalk period is +the great development of Ammonites and other Cephalopods +in the Lower Chalk, and of sea urchins and other +echinoderms in the Upper, while the Middle Chalk is +wanting in the one and the other. Shark's teeth tell of +the larger inhabitants of the ocean that flowed above the +chalky bottom.</p> + +<p>Many quarries have been opened on the flanks of the +Chalk Downs, of which a large number are now disused. +They occur just where they are needed for chalk to lay +on the land, the pure chalk on the north of the Downs to +break up the heavy Tertiary clays, which largely cover +the north of the Island; the more clayey beds of the Grey +Chalk on the south of the downs to stiffen the light loams +of the Greensand.<a name="FNanchor_A_10" id="FNanchor_A_10"></a><a href="#Footnote_A_10" class="fnanchor">[10]</a></p> + +<div class="footnote"><p><a name="Footnote_A_8" id="Footnote_A_8"></a><a href="#FNanchor_A_8"><span class="label">[8]</span></a> See <i>Common Stones</i>, by Grenville A. J. Cole, F.R.S. 1921.</p></div> + +<div class="footnote"><p><a name="Footnote_A_9" id="Footnote_A_9"></a><a href="#FNanchor_A_9"><span class="label">[9]</span></a> 1,472 ft. at the western end of the Island, 1,213 ft. at the eastern.—Dr. +Rowe's measurements.</p></div> + +<div class="footnote"><p><a name="Footnote_A_10" id="Footnote_A_10"></a><a href="#FNanchor_A_10"><span class="label">[10]</span></a> Dr. A. W. Rowe.</p></div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_54" id="Page_54">[Pg 54]</a></span></p> + +<div class="chapt_hdr">Chapter VIII</div> + +<div class="chapt_ttl">THE TERTIARY ERA: THE EOCENE</div> + +<p>Ages must have passed while the ocean flowed over this +part of the world, and the chalk mud, with its varied +remains of living things, gradually accumulated at the +bottom. At last a change came. Slowly the sea bed +rose, till the chalk, now hardened by pressure, was raised +into land above the sea level. As soon as this happened, +sea waves and rain and rivers began to cut it down. +There is evidence here of a wide gap in the succession of +the strata. Higher chalk strata, which probably once +existed, have been washed away, while the underlying +strata have been planed off to an even surface more or +less oblique to the bedding-planes. The highest zone of +the chalk in the Island (that of <i>Belemnitella macronata</i>) +varies greatly in thickness, from 150 ft. at the eastern end +of the Island to 475 at the western. The latest investigations +give reason to conclude that this is due to gentle +synclines and anticlines, which have been planed smooth +by the erosion which preceded the deposition of the next +strata,—the Eocene.<a name="FNanchor_A_11" id="FNanchor_A_11"></a><a href="#Footnote_A_11" class="fnanchor">[11]</a> At Alum Bay the eroded surface +of the chalk may be seen with rolled flints lying upon it, +and rounded hollows or pot-holes, the appearance being +that of a foreshore worn in a horizontal ledge of rock, +much like the Horse Ledge at Shanklin.</p> + +<p>The land sank again, but not to anything like the depth +of the great Chalk Sea. We now come to an era called +the Tertiary. The whole geological history is divided +<span class='pagenum'><a name="Page_55" id="Page_55">[Pg 55]</a></span> +into four great eras. The first is the Eozoic, or the age +of the Archæan,—often called Pre-Cambrian—rocks; +rocks largely volcanic, or greatly altered since their +formation, showing only obscure traces of the life which +no doubt existed. Then follow the Primary era, or, as +it is generally called, the Palæozoic; the Secondary or +Mesozoic; and the Tertiary or Kainozoic. Palæozoic is +used rather than Primary, as this word is ambiguous, +being also used for the crystalline rocks first formed by +the solidification of the molten surface of the earth. +But Secondary and Tertiary are still in constant use. +These long ages, or eras, were of very unequal duration; +yet they mark such changes in the life of animal and +plant upon the earth that they form natural divisions. +The Palæozoic was an immense period during which life +abounded in the seas,—numberless species of mollusca, +crustaceans, corals, fish are found,—and there were great +forests, which have formed the coal measures, on land,—forests +of strange primeval vegetation, but in which +beautiful ferns, large and small, flourished in great +numbers. The Secondary Era may be called the age of +reptiles. To this era all the rocks we have so far studied +belong. Now we come to the last era, the Tertiary, the +age of the mammals. Instead of reptiles on land, in sea +and air, we find a complete change. The earth is occupied +by the mammalia; the air belongs to the birds such +as we see to-day. The strange birds of the Oolitic +and Cretaceous have passed away. Birds have taken +their modern form. In some parts of the world +strata are found transitional between the Secondary and +Tertiary.</p> + +<p>The Tertiary is divided into four divisions,—the Eocene, +the Oligocene (once called Upper Eocene), the Miocene, +and the Pliocene; which words signify,—Pliocene the +more recent period, Miocene the less recent, Eocene the +dawn of the recent.</p> + +<p><span class='pagenum'><a name="Page_56" id="Page_56">[Pg 56]</a></span> +In the Eocene we shall find marine deposits of a comparatively +shallow sea, and beds deposited at the mouth +of great rivers, where remains of sea creatures are mingled +with those washed down from the land by the rivers. +These strata run through the Isle of Wight from east to +west, and we may study them at either end of the Island, +in Whitecliff and Alum Bays. The strata are highly +inclined, so that we can walk across them in a short walk. +Some beds contain many fossils, but many of the shells +are very brittle and crumbly; and we can only secure +good specimens by cutting out a piece of the clay or sand +containing them, and transferring them carefully to +boxes, to be carried home with equal care. Often much +of the face of the cliff is covered with slip or rainwash, +and overgrown with vegetation. Sometimes a large slip +exposes a good hunting ground.</p> + +<p>Now let us walk along the shore, and try to read the +story these Tertiary beds tell us. We will begin in +Whitecliff Bay. Though easily accessible, it remains still +in its natural beauty. The sea washes in on a fine stretch +of smooth sand sheltered by the white chalk wall which +forms the south arm of the bay. North of the Culver +downs the cliffs are much lower, and consist of sands and +clays of varying colour, following each other in vertical +bands. Looking along the line of shore we notice a band +of limestone, at first nearly vertical like the preceding +strata, then curving at a sharp angle as it slopes to the +shore, and running out to sea in a reef known as Bembridge +Ledge. This is the Bembridge limestone; and +the beginning of the reef marks the northern boundary of +Whitecliff Bay, the shore, however, continuing in nearly +the same line to Bembridge Foreland, and showing a +continuous succession of Eocene and Oligocene strata. +The strata north of the limestone are nearly horizontal, +dipping slightly to the north. In the Bembridge limestone +we see the end of the Sandown anticline, and the +beginning of the succeeding syncline. The strata now +dip under the Solent, and rise into another anticline in +the Portsdown Hills. North and south of the great +anticline of the Weald of Kent and Sussex are two synclinal +troughs known as the London and Hampshire +basins. Nearly the whole of our English Eocene strata +lies in these two basins, having been denuded away from +the anticlinal arches. The Oligocene only occur in the +Hampshire basin, the higher strata only in the Isle of +Wight.</p> +<p> </p> +<p> </p> + +<a name="Fig_3" id="Fig_3"></a> +<div class="text_rt smcap">Fig. 3</div> + +<div class="center"> + <div style="width: 597px" class="figcenter"> + <img src="images/fig_3.png" width="597" height="140" title="Coast Section, Whitecliff Bay." alt="Coast Section, Whitecliff Bay." /> + </div> + <table class="smaller" summary="Strata List"> + <tr><td colspan=8 class="center">COAST SECTION, WHITECLIFF BAY.</td></tr> + <tr><td colspan=8> </td></tr> + <tr><td>BM</td><td><i>Bembridge Marls.</i></td><td> </td><td>B</td><td><i>Barton Clay.</i></td><td> </td><td>Ch</td><td><i>Chalk.</i></td></tr> + <tr><td>BL</td><td><i>Bembridge Limestone.</i></td><td> </td><td>Br</td><td><i>Bracklesham Beds.</i></td><td> </td><td>P</td><td><i>Pebble Beds.</i></td></tr> + <tr><td>O</td><td><i>Osborne Beds.</i></td><td> </td><td>Bg</td><td><i>Bagshot Beds.</i></td><td> </td><td>S</td><td><i>Sandstone Band.</i></td></tr> + <tr><td>H</td><td><i>Headon Beds.</i></td><td> </td><td>L</td><td><i>London Clay.</i></td><td> </td><td> </td></tr> + <tr><td>BS</td><td><i>Barton Sand.</i></td><td> </td><td>R</td><td><i>Reading Beds.</i></td><td> </td><td> </td></tr> + </table> +</div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_57" id="Page_57">[Pg 57]</a></span> +Above the Chalk we come first to a thick red clay called +Plastic clay. It is much slipped, and the slip is overgrown. +The only fossils found in the Island are fragments +of plants; larger plant remains on the mainland show a +temperate climate. This clay was formerly worked at +Newport for pottery. The clay is probably a freshwater +deposit formed in fairly deep water. On the mainland +we find on the border shallow water deposits called the +Woolwich and Reading beds. (The clay is 150 to 160 ft. +thick at Whitecliff Bay, less than 90 ft. at the Alum Bay.) +We come next to a considerable thickness of dark clay +with sand, at the surface turned brown by weathering. +This is the London clay, so called because it underlies the +area on which London is built. At the base is a band of +rounded flint pebbles, which extends at the base of the +clay from here to Suffolk. In it, as well as in a hard +sandstone 18 inches higher up, are tubular shells of a +marine worm, <i>Ditrupa plana</i>. The sandstone runs out +on the shore. About 35 ft. above the basement bed is a +zone of <i>Panopæa intermedia</i> and <i>Pholadomya margaritacea</i>, +at 50 ft. another band of <i>Ditrupa</i>, and at about +80 ft. a band with a small <i>Cardita</i>. In the higher part of +the clay are large septaria,—rounded blocks of a calcareous +clay-ironstone, with cracks running through them +filled with spar. <i>Pinna affinis</i> is found in the septaria. +The thickness of the clay in Whitecliff Bay is 322 feet. +<span class='pagenum'><a name="Page_58" id="Page_58">[Pg 58]</a></span> +It can be seen on the shore, when the tide happens to +have swept the sand away. Otherwise the lower beds are +hardly visible, there being no cliff here, but a slope overgrown +with vegetation.</p> + +<p>In Alum Bay the London clay, about 400 ft. in thickness, +consists of clays, chiefly dark blue, with sands, and +lines of septaria. In the lower part is a dark clay with +<i>Pholadomya margaritacea</i>, still preserving the pearly +nacre. There are also <i>Panopæa intermedia</i>, and in septaria +<i>Pinna affinis</i>. All these with their pearly lustre, +are beautiful fossils. A little higher is a zone with +<i>Ditrupa</i>, and further on a band of <i>Cardita</i>. Other shells +also are found in the clay, especially in the lower part. +They are all marine, and indicate a sub-tropical climate. +Lines of pebbles show that we are near a beach. In other +parts of the south of England remains from the land are +found, borne down an ancient river in the way we found +before in the Wealden deposits.</p> + +<p>But times have changed since the Wealden days, and +the life of the Tertiary times has a much more modern +appearance. From leaves and fruits borne down from +the forest we can learn clearly the nature of the early +Eocene land and climate. Leaves are found at Newhaven, +and numerous fossil fruits at Sheppey. The character of +the vegetation most resembled that now to be seen in India, +South Eastern Asia, and Australia. Palms grew luxuriantly, +the most abundant fruit being that of one called +Nipadites, from its resemblance to the Nipa palm, which +grows on the banks of rivers in India and the Philippines. +The forests also included plants allied to cypresses, +banksia, maples, poplars, mimosa, custard apples, gourds, +and melons. The rivers abounded in turtle—large +numbers of remains of which are found in the London +clay at the mouth of the Thames—crocodiles and alligators. +With the exception of the south east of England, +all the British Isles formed part of a continental mass of +land covered with a tropical vegetation. The mountain +chains of England, Scotland, and Wales rose as now, but +higher. Long denudation has worn them down since. +In the south-east of England the coast line fluctuated; +and sea shells, and the remains of the plant and animal +life of the neighbourhood of a great tropical river alternate +in the deposits.</p> +<p> </p> +<p> </p> + +<a name="Fig_4" id="Fig_4"></a> +<div class="text_rt smcap">Fig. 4</div> + +<div class="center"> + <div style="width: 598px" class="figcenter"> + <img src="images/fig_4.png" width="598" height="98" title="Section Through Headon Hill And High Down. Showing Strata Seen At Alum Bay." alt="Section Through Headon Hill And High Down." /> + </div> + <table class="smaller" summary="Strata List"> + <tr><td colspan=10>SECTION THROUGH HEADON HILL AND HIGH DOWN. SHOWING STRATA SEEN AT ALUM BAY.</td></tr> + <tr><td> </td><td>G</td><td><i>Gravel Cap.</i></td><td> </td><td>LH</td><td><i>Lower Headon.</i></td><td> </td><td>L</td><td><i>London Clay.</i></td><td> </td></tr> + <tr><td> </td><td>Bm</td><td><i>Bembridge Limestone.</i></td><td> </td><td>BS</td><td><i>Barton Sand.</i></td><td> </td><td>R</td><td><i>Reading Beds.</i></td><td> </td></tr> + <tr><td> </td><td>O</td><td><i>Osborne Beds.</i></td><td> </td><td>B</td><td><i>Barton Clay.</i></td><td> </td><td>Ch</td><td><i>Chalk.</i></td><td> </td></tr> + <tr><td> </td><td>UH</td><td><i>Upper Headon.</i></td><td> </td><td>Br</td><td><i>Bracklesham Beds.</i></td><td> </td><td> </td><td> </td><td> </td></tr> + <tr><td> </td><td>MH</td><td><i>Middle "</i></td><td> </td><td>Bg</td><td><i>Bagshot Sands.</i></td><td> </td><td> </td><td> </td><td> </td></tr> +</table> +</div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_59" id="Page_59">[Pg 59]</a></span> +The London clay is succeeded by a great thickness of +sands and clays which form the Bagshot series. These +are divided in the London basin into Lower, Middle, and +Upper Bagshot. In the Hampshire basin the strata are +now classified as Bagshot Sands, Bracklesham Beds, +Barton Beds, the last comprising the Barton Clay and the +Barton Sand, formerly termed Headon Hill Sands. There +is some uncertainty as to the manner in which these correspond +to the beds of the Bagshot district, as the Tertiary +strata have been divided by denudation into two groups, +and differ in character in the two areas. It is possible +that the Barton Sand represents a later deposit than +any in the London area.</p> + +<p>Almost the only fossil remains in the Bagshot Sands +are those of plants, but these are of great interest. In +Whitecliff Bay the beds consist for the most part of +yellow sands, above which is a band of flint pebbles, which +has been taken as the base of the Bracklesham series, for +in the clay immediately above marine shells occur. The +Bagshot Sands, in Whitecliff Bay, are about 138 feet +thick, in Alum Bay, 76 feet, according to the latest +classification. In Alum Bay the strata consist of sands, +yellow, grey, white, and crimson, with clays, and bands +of pipe clay. This is remarkably white and pure, as +though derived from white felspar, like the China clay in +Cornwall. The pipe clay contains leaves of trees, sometimes +beautifully preserved. Specimens are not very +easy to obtain, as only the edges of the leaves appear at +the surface of the cliff. They have been found chiefly +<span class='pagenum'><a name="Page_60" id="Page_60">[Pg 60]</a></span> +in a pocket, or thickening of the seam of pipe clay, which +for forty years yielded specimens abundantly, afterwards +thinning out, when the leaves became rare. The leaves +lie flat, as they drifted and settled down in a pool. With +them are the twigs of a conifer, occasionally a fruit or +flower, or the wing case of a beetle. The leaves show a +tropical climate. The flora is a local one, differing considerably +from those of Eocene deposits elsewhere. The +plants are nearly all dicotyledons. Of palms there are +only a few fragments, while the London clay of Sheppey +is rich in palm fruits, and many large palms are found +in the Bournemouth leaf beds, corresponding in date to +the Bracklesham. The differences may be largely due to +conditions of locality and deposition. The Alum Bay +flora is characterised by a wealth of leguminous plants, +and large leaves of species of fig (<i>Ficus</i>); simple laurel +and willow-like leaves are common, of which it is difficult +to determine the species, and there is abundance of a +species of <i>Aralia</i>. The character of the flora resembles +most those of Central America and the Malay Archipelago.</p> +<p> </p> +<p> </p> + +<a name="Plate_IV" id="Plate_IV"></a> +<div class="smcap text_rt">PL. IV</div> +<div class="center"> +<table width="100%" class="center" summary="Eocene And Oligocene Fossils"> + <tr> + <td valign="bottom"><img src="images/cleardot.png" width="0" height="200" title="" alt="" /><img src="images/pl_iv_turritella.png" width="62" height="123" title="" alt="" /><br /><span class="smaller smcap">Turritella<br />Imbricataria</span></td> + <td valign="top"><img src="images/pl_iv_numulites.png" width="54" height="48" title="" alt="" /><br /><span class="smaller smcap">Nummulites<br />Lævigatus</span></td> + <td valign="bottom"><img src="images/pl_iv_limnaea.png" width="57" height="119" title="" alt="" /><br /><span class="smaller smcap">Limnæa<br />Longiscata</span></td> + </tr><tr> + <td colspan=3 class="center"><img src="images/pl_iv_cardita.png" width="193" height="171" title="" alt="" /><br /><span class="smaller smcap">Cardita Planicosta</span></td> + </tr><tr> + <td valign="top"><img src="images/pl_iv_fusus.png" width="84" height="108" title="" alt="" /><br /><span class="smaller smcap">(Fusus)<br />Leiostama Pyrus</span></td> + <td valign="bottom"><img src="images/cleardot.png" width="0" height="250" title="" alt="" /><img src="images/pl_iv_cyrena.png" width="100" height="76" title="" alt="" /><br /><span class="smaller smcap">Cyrena Semistriata</span><br /> + <td valign="top"><img src="images/pl_iv_planorbis.png" width="102" height="94" title="" alt="" /><br /><span class="smaller smcap">Planorbis Euomphalus</span></td> +</table> +<div class="caption4">EOCENE AND OLIGOCENE</div> +</div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_61" id="Page_61">[Pg 61]</a></span> +The Bracklesham Beds in Alum Bay (570 ft. thick) +consist of clays, with lignite forming bands 6 in. to 2 ft. +thick; white, yellow, and crimson sands; and in the +upper part dark sandy clays, with bands showing impressions +of marine fossils. Alum Bay takes its name from +the alum formerly manufactured from the Tertiary clays. +The coloured sands have made the bay famous. The colours +of the sands when freshly exposed, and of the cliffs when wet +with rain, are very rich and beautiful,—deep purple, crimson, +yellow, white, and grey. Some of the beds are finely +striped in different shades by current bedding. The +contrast of these coloured cliffs with the White Chalk, +weathered to a soft grey, of the other half of the bay is +very striking and beautiful. About 45 ft. from the top is +a conglomerate of flint pebbles, some of large size, +cemented by iron oxide. In Whitecliff Bay the Bracklesham +Beds (585 ft.) consist of clays, sands, and sandy +clays, mostly dark, greenish and blue in colour, containing +marine fossils and lignite. Sir Richard Worsley, in his +History of the Isle of Wight, tells that in February, 1773, +a bed of coal was laid bare in Whitecliff Bay, causing +great excitement in the neighbourhood. People flocked +to the shore for coal, but it proved worthless as fuel. It +has, however, been worked to some extent in later years. +In some of the beds are many fossils. Numbers have +lately been visible where a large founder has taken place. +There are large shells of <i>Cardita planicosta</i> and <i>Turritella +imbricataria</i>. They are, however, very fragile. In a +stratum just above these are numbers of a large Nummulite +(<i>Nummulites lævigatus</i>). These are round flat shells +like coins,—hence the name (Lat. <i>nummus</i>, a coin). They +are a large species of foraminifera. We may split them +with a penknife; and then we see a pretty spiral of tiny +chambers. A smaller variety, <i>N. variolarius</i>, occurs a +little further on, and a tiny kind, <i>N. elegans</i>, in the +Barton clay. One of the most striking features of +the later Eocene is the immense development of +Nummulite limestones—vast beds built up of the +delicate chambered shells of Nummulites,—which extend +from the Alps and Carpathians into Thibet, and from +Morocco, Algeria, and Egypt, through Afghanistan and +the Himalaya to China. The pyramids of Egypt are +built of this limestone.</p> + +<p>The Bracklesham beds are followed by the Barton clay, +famous for the number of beautiful fossil shells found +at Barton on the Hampshire coast. At Whitecliff Bay +the fossils are, unfortunately, very friable. At Alum +Bay the pathway to the shore is in a gully in the upper +part of the Barton clay. The strata consist of clays, +sands, and sandy clays. The base of the beds is marked +by the zone of <i>Nummulites elegans</i>. Numerous very +<span class='pagenum'><a name="Page_62" id="Page_62">[Pg 62]</a></span> +pretty shells of the smaller Barton types may be found, +with fragments of larger ones; or a whole one may be +found. Owing to the cliff section cutting straight across +the strata, which are nearly vertical, there is far less of +the beds open to observation than at Barton, which +probably accounts for the list of fossils being much smaller. +The shells are chiefly several species of <i>Pleurotoma</i>, <i>Rostellaria</i>, +<i>Fusus</i>, <i>Voluta</i>, <i>Turritella</i>, <i>Natica</i>, a small bivalve +<i>Corbula pisum</i>, a tubular shell of a sand-boring mollusc +<i>Dentalium</i>, <i>Ostrœa</i>, <i>Pecten</i>, <i>Cardium</i>, <i>Crassatella</i>. The +fauna is like a blending of Malayan and New Zealand +forms of marine life. Throughout the Eocene from the +London clay onward the shells are such as abound in the +warm sea south east of Asia. Similarly the plant remains +take us into a tropic land, where fan palms and feather +palms overshadowed the country, trees of the tropics +mingling with trees we still find in more Northern latitudes. +The general character of the flora as of the shells was +Oriental and Malayan; both being succeeded in later +strata by a flora and fauna with greater analogy to that +now existing in Western North America.</p> + +<p>In Alum Bay the Barton clay is suddenly succeeded +by the very fine yellow and white sands which run along +the western base of Headon Hill, the curve of the syncline +bringing them round from a nearly vertical to an almost +horizontal position. These are now known as the Barton +Sand. They are 90 ft. thick, the whole of the Barton +beds being 338 ft. in Alum Bay, 368 ft. in Whitecliff. +The sands were formerly extensively used for glass making. +They are almost unfossiliferous. The passage from Barton +clay to the sands in Whitecliff Bay is more gradual. The +sands here show some fine colouring which reminds us of +the more celebrated sands of Alum Bay.</p> + +<div class="footnote"><p><a name="Footnote_A_11" id="Footnote_A_11"></a><a href="#FNanchor_A_11"><span class="label">[11]</span></a> See Memoir of Geological Survey of I. W. by H. J. Osborne +White, F.G.S. 1921, p. 90.</p></div> + +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_63" id="Page_63">[Pg 63]</a></span></p> + +<div class="chapt_hdr">Chapter IX</div> + +<div class="chapt_ttl">THE OLIGOCENE</div> + +<p>We pass on to strata which used to be called Upper +Eocene, but are now generally classified as a period by +themselves, and called the Oligocene. They are also +known as the Fluvio-marine series. Large part was +deposited in freshwater by rivers running into lagoons, +or in the brackish water of estuaries, while at times the +sea encroached, and beds of marine origin were laid down.</p> + +<p>The west of the Island is much the best locality for the +lower strata, those which take their name from Headon +Hill between Alum and Totland Bays. There are three +divisions of the Headon strata, marine beds in the middle +coming between upper and lower beds formed in fresh +and brackish water. Light green clays are very characteristic +of these beds, and at the west of the Island thick +freshwater limestones, which have died out before the +strata re-appear in Whitecliff Bay. The strongest masses +of limestone in Headon Hill belong to the Upper division. +The limestones are full of freshwater shells, nearly all the +long spiral Limnæa and the flat spiral disc of Planorbis, +perhaps the most abundant species being <i>L. longiscata</i> +and <i>P. euomphalus</i>. The limestones themselves are almost +entirely the produce of a freshwater plant <i>Chara</i>, which +precipitates lime on its tissues, in the same manner as the +sea weeds we call corallines. On the shore round the base +of Headon Hill lie numerous blocks of limestone, the +débris of strata fallen in confusion, in which are beautiful +specimens of Limnæa and Planorbis. The shells, however, +are very fragile. The marine beds of the Middle Headon +<span class='pagenum'><a name="Page_64" id="Page_64">[Pg 64]</a></span> +are best seen in Colwell Bay, where a few yards north +of How Ledge they descend to the beach, and a cliff +is seen formed of a thick bed of oysters, <i>Ostrea velata</i>. +The oysters occupy a hollow eroded in a sandy clay +full of <i>Cytherea incrassata</i>, from which the bed is known +as the "Venus" bed, the shell formerly being called +<i>Venus</i>, later <i>Cytherea</i>, at present <i>Meretrix</i>. The marine +beds contain many drifted freshwater shells as Limnæa +and Cyrena. The How Ledge limestone forms the top +of the Lower Headon. It is full of well-preserved +Limnæa and Planorbis.</p> + +<p>The Upper and Lower Headon are mainly fresh or +brackish water deposits. The purely freshwater beds +contain <i>Limnæa</i>, <i>Planorbis</i>, <i>Paludina</i>, <i>Unio</i>, and land-shells. +In the brackish are found <i>Potamomya</i>, <i>Cyrena</i>, +<i>Cerithium</i> (<i>Potamides</i>), <i>Melania</i> and <i>Melanopsis</i>. <i>Paludina +lenta</i> is very abundant throughout the Oligocene. +A large number of the marine shells of the Headon beds +are species also found in the Barton clay. <i>Cytherea</i>, +<i>Voluta</i>, <i>Ancillaria</i>, <i>Pleurotoma</i>, <i>Natica</i> are purely marine +genera.</p> + +<p>In White Cliff Bay the beds are mostly estuarine. Most +of the fossils are found in two bands, one about 30 ft. +above the base of the series, the other a stiff blue clay, +about 90 feet higher, which seems to correspond with the +"Venus Bed" of Colwell Bay. Many of the fossils are of +Barton types.</p> + +<p>The Headon beds are about 150 feet thick at Headon +Hill, 212 ft. in Whitecliff Bay; and are followed by beds +varying from about 80 to 110 ft. in thickness, known as +the Osborne and St. Helens series. They consist mainly +of marls variously coloured, with sandstone and limestone. +In Headon Hill is a thick concretionary limestone, +which almost disappears northward. The Oligocene +strata often vary considerably within short distances. +The Osborne beds are exposed along the low shore between +<span class='pagenum'><a name="Page_65" id="Page_65">[Pg 65]</a></span> +Cowes and Ryde, and from Sea View to St. Helens. In +Whitecliff Bay they are not well seen, occurring in overgrown +slopes. They consist mostly of red and green clays. +A band of cream-yellow limestone a foot thick is the most +conspicuous feature. The fossils resemble those from +the Headon beds, but are much less plentiful. The marls +seem to have been mostly deposited in lagoons of brackish +water, which at the present day are favourite places for +turtles and alligators, and of these many remains are +found in the Osborne beds. The beds are specially noted +for the shoals of small fish, <i>Diplomystus vectensis</i> (<i>Clupea</i>), +first observed by Mr. G. W. Colenutt, F.G.S., and +prawns found in them, and also remains of plants. +The beds that appear in the neighbourhood of Sea +View and St. Helens are divided into Nettlestone Grits +and St. Helen's Sands, the former containing a freestone +8 feet thick.</p> + +<p>Above these beds lies the Bembridge limestone, which +is so conspicuous in Whitecliff Bay, and forms Bembridge +Ledge. On the north shore of the Island the strata rise +slightly on the northern side of the syncline. There are +also minor undulations in an east and west direction. +The result is to bring up the Bembridge limestone at +various points along the north shore, where it forms +conspicuous ledges—Hamstead Ledge at the mouth of +the Newtown river, ledges in Thorness Bay, and Gurnard +Ledge. In Whitecliff Bay the limestone, about 25 feet +thick, forms the conspicuous reef called Bembridge Ledge. +The Bembridge limestone consists of two or more bands +of limestone with intercalated clays. It is usually whiter +than the Headon limestones, and the fossils occur as casts, +the shells being sometimes replaced by calc-spar. The +limestone has been much used as a building stone for +centuries, not only in the Island, but for buildings on the +mainland. The most famous quarries were those near +Binstead, from which Quarr, the site of the great Abbey, +<span class='pagenum'><a name="Page_66" id="Page_66">[Pg 66]</a></span> +now almost entirely disappeared, derives its name. From +these quarries was obtained much of the stone for Winchester +Cathedral and many other ancient buildings. In +the old walls and buildings of Southampton the stone may +be recognised at once by the casts of the Limnæae it +contains. The quarries at Quarr were noted in more ways +than one. In later times the remains of early mammalia,—Palæotherium, +Anoplotherium, and others—have been +found. The quarries are now abandoned and overgrown. +The limestone may be seen inland at Brading, where it +forms the ridge on which the Church stands.</p> + +<p>The limestone is a freshwater formation, and the fossils +are mostly freshwater shells, of the same type as the +Headon, Limnæa and Planorbis the most common. +There are also land shells, especially several species of +Helix, the genus which includes the common snail,—<i>H. +globosa</i>, very large,—and great species of <i>Bulimus</i> (<i>Amphidromus</i>) +and <i>Achatina</i> (<i>B. Ellipticus</i>, <i>A. costellata</i>). +These interesting shells were chiefly obtained in the limestone +at Sconce near Yarmouth, a locality now inaccessible, +being occupied by fortifications. The land shells have an +affinity to species now found in Southern North America. +The limestone also abounds in the so-called "seeds" of +Chara. The reproductive organs,—the "seeds,"—of +this curious water-plant, allied to the lower Algæ, are, like +the rest of the plant, encased in carbonate of lime, and +are very durable. Large numbers are found in the +Oligocene strata. Under the microscope they are seen +to be beautifully sculptured in various designs, with a +delicate spiral running round them. Above the limestone +lie the Bembridge marls, varying in thickness in different +localities from 70 to 120 feet. North of Whitecliff Bay +they stretch on to the Foreland. They are in the main +a freshwater formation, but a few feet above the limestone +is a marine band with oysters, <i>Ostrea Vectensis</i>. It runs +out along the shore, where the oysters may be seen covering +<span class='pagenum'><a name="Page_67" id="Page_67">[Pg 67]</a></span> +the surface. The Lower Marls consist chiefly of variously-coloured +clays with many shells, chiefly <i>Cyrena pulchra</i>, +<i>semistriata</i>, and <i>obovata</i>, <i>Cerithium mutabile</i>, and <i>Melania +muricata</i> (<i>acuta</i>); and red and green marls, in which are +few shells, but fragments of turtle occur. A little above +the oyster bed is a band of hard-bluish septarian limestone. +Sixty years ago Edward Forbes remarked on the resemblance +of this band to the harder insect-bearing +limestones of the Purbeck beds. In a limestone exactly +resembling this, and similarly situated in the lower part +of the marls in Gurnard and Thorness Bays, numerous +insects were afterwards found,—beetles, flies, locusts, and +dragonflies, and spiders. Leaves of plants, including +palms, fig, and cinnamon, have also been found in this +bed, showing that the climate was still sub-tropical. +The upper Marls consist chiefly of grey clays with abundance +of <i>Melania turritissima</i> (<i>Potamaclis</i>). The chief +shells in the marls are <i>Cyrena</i>, <i>Melania</i>, <i>Melanopsis</i> +and <i>Paludina</i> (<i>Viviparus</i>). They are often beautifully +preserved; the species of Cyrena often retain their colour-markings.</p> + +<p>Bembridge Foreland is formed by a thick bed of flint +gravel resting on the marls, which are seen again in Priory +Bay, where in winter they flow over the sea-wall in a semi-liquid +condition. They lie above the limestone at Gurnard, +Thorness, and Hamstead. West of Hamstead Ledge +the whole of the beds crop out on the shore, where beautifully +preserved fossils may be collected. Large pieces of +drift wood occur, also seeds and fruit. Many fragments +of turtle plates may be found. Large crystals of selenite +(sulphate of lime) occur in the Marls.</p> + +<p>Last of the Oligocene in the Isle of Wight are the +Hamstead beds. These strata are peculiar to the Isle of +Wight. The Bembridge beds also are not found on the +mainland, except a small outlier at Creechbarrow Hill +in Dorset. The Hamstead beds consist of some 250 feet +<span class='pagenum'><a name="Page_68" id="Page_68">[Pg 68]</a></span> +of marls, in which many interesting fossils have been +found. They cover a large area of the northern part of +the Island, largely overlaid by gravels, and are only seen +on the coast at Hamstead, where they form the greater +part of the cliff, which reaches a height of 210 ft., the top +being capped by gravel. In winter the clays become +semi-liquid, in summer the surface may be largely slip +and rainwash, baked hard by the sun. The lower part +of the strata may be best seen on the shore. The strata +consist of 225 ft. of freshwater, estuarine, and lagoon +beds, with <i>Unio</i>, <i>Cyrena</i>, <i>Cyclas</i>, <i>Paludina</i>, <i>Hydrobia</i>, +<i>Melania</i>, <i>Planorbis</i>, <i>Cerithium</i> (rare), and remains of +turtles, crocodiles, and mammals, leaves and seeds of +plants; and above these beds 31 feet of marine beds with +<i>Corbula</i>, <i>Cytherea</i>, <i>Ostrea callifera</i>, <i>Cuma</i>, <i>Voluta</i>, <i>Natica</i>, +<i>Cerithium</i>, and <i>Melania</i>.</p> + +<p>Except for the convenience of dividing so large a mass +of strata, it would not be necessary to divide these from +the Bembridge beds, as no break in the character of the +life of the period occurs at the junction. The basement +bed of the Hamstead strata is known as the Black Band, +2 feet of clay, coloured black with vegetable matter, with +<i>Paludina lenta</i> very numerous, <i>Melanopsis carinata</i>, +<i>Limnæa</i>, <i>Planorbis</i>, a small <i>Cyclas</i> (<i>C. Bristovii</i>), seed +vessels, and lumps of lignite. It rests on dark green marls +with <i>Paludina lenta</i> and <i>Melanopsis</i>, and full of roots. +This evidently marks an old land surface. About 65 feet +higher is the White Band,—a white and green clay full +of shells, mostly broken. There are bands of tabular +ironstone containing <i>Paludina lenta</i>. Clay ironstone was +formerly collected on the shore between Yarmouth and +Hamstead and sent to Swansea to be smelted. The +strata consist largely of mottled green and red clays, +probably deposited in brackish lagoons. These yield +few fossils except remains of turtle and crocodile and drifted +plants. The blue clays are much more fossiliferous. +Among other plants are leaves of palm and water-lily. +<span class='pagenum'><a name="Page_69" id="Page_69">[Pg 69]</a></span> +The strata gradually become more marine upwards. +The marine beds were called by Forbes the Corbula beds, +from two small shells, <i>C. pisum</i> and <i>C. vectensis</i>, of which +some of the clays are full. Remains of early mammalia +are found in the Hamstead beds, the most frequent being +a hog-like animal, of supposed aquatic habits, Hyopotamus, +of which there are more than one species.</p> + +<p>The fauna and flora of the Oligocene strata show that +the climate was still sub-tropical, though somewhat +cooling down from the Eocene. Palms grew in what is now +the Isle of Wight. Alligators and crocodiles swam in the +rivers. Turtle were abundant in river and lagoon. +Specially interesting in the Eocene and Oligocene are the +mammalian remains. They show us mammals in an +early stage before they branched off into the various +families as we know them to-day. The Palæotherium +was an animal like the tapir, now an inhabitant of the +warmer <a name="regions"></a><a href="#typos">regions</a> of Asia and America. Recent discoveries +in Eocene strata in Egypt show stages of development +between a tapir-like animal and the elephant with long +trunk and tusks. There were in those days hog-like +animals intermediate between the hogs and the hippopotami. +There were ancestors of the horse with three toes +on each foot. There were hornless ancestors of the deer +and antelopes. Many of the early mammals showed +characters now found in the marsupials, the order to which +the Kangaroo and Opossum belong, members of which +are found in rocks of the Secondary Era, and are the only +representatives of the mammalia in that age. Some of +the early Eocene mammalia are either marsupials, or +closely related to them. In the Oligocene we find the +mammalian life becoming more varied, and branching out +into the various groups we know to-day; while the +succeeding Miocene Period witnesses the culmination of +the mammalia—mammals of every family abounding all +over the earth's surface, in a profusion and variety not +seen before—or since, outside the tropics.</p> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_70" id="Page_70">[Pg 70]</a></span></p> + +<div class="chapt_hdr">Chapter X</div> +<div class="chapt_ttl">BEFORE AND AFTER.—THE ICE AGE.</div> + + +<p>We have read the story written in the rocks of the Isle of +Wight. What wonderful changes we have seen in the +course of the long history! First we were taken back to +the ancient Wealden river, and saw in imagination the +great continent through which it flowed, and the strange +creatures that lived in the old land. We saw the delta +sink beneath the sea, and a great thickness of shallow +water deposits laid down, enclosing remains of ammonites +and other beautiful forms of life. Then long ages passed +away, while in the waters of a deeper sea the great thickness +of the chalk was built up, mainly by the accumulation +of microscopic shells. In time the sea bed rose, and new +land appeared, and another river bore down fruits to be +buried with sea shells and remains of turtles and crocodiles +in the mud deposited near its mouth to form the +London clay. We followed the alternations of sea and +land, and the changing life of Eocene and Oligocene times. +We have heard of the early mammalia found in the quarries +of Quarr, and have learnt from the leaf beds of Alum Bay +that at that time the climate of this part of the world was +tropical. Indeed, I think everything goes to prove that +through the whole of the times we have been studying,—except +perhaps the earliest Eocene, that of the Reading +beds,—the climate was considerably warmer than it is +at the present day. After all these changes do you not +want to know what happened next? Well, at this point +we come to a gap in the records of the rocks, not only in +the Isle of Wight, but also in the British Isles. The +<span class='pagenum'><a name="Page_71" id="Page_71">[Pg 71]</a></span> +British Isles, or even England and Wales alone, are almost, +if not quite unique in the world in that, in their small +extent, they contain specimens of nearly every formation +from the most ancient times to the present day. In +other parts of the world we may find regions many times +this area, where we can only study the rocks of some one +period. But just at this point in the story comes a period,—a +very important one, too,—the Miocene—of which we +have no remains in our Islands. We must hear a little +of what happened before we come back to the Isle of +Wight again in comparatively recent times.</p> + +<p>But, first, perhaps, I had better tell,—just in outline,—something +of the earlier history of the world, before any +of our Isle of Wight rocks were made. For, if I do not, +quite a wrong idea may be formed of the world's history. +The time of the Wealden river has seemed to us very +ancient. We cannot say how many hundreds of +thousands, or rather millions of years have passed since +that ancient Wealden age. And you may have thought +that we had got back then very near the world's birthday, +and were looking at some of the oldest rocks on the +globe. But no. We are not near the beginning yet. +Compared with the vast ages that went before, our Wealden +period is almost modern. We cannot tell with any +certainty the comparative time; but we may compare +the thickness of strata formed to give us some sort of idea. +Now to the first strata in which fossil remains of living +things are found we have in all a thickness of strata some +12 times that of all the rocks we have been studying from +Wealden to Oligocene, together with the later rocks, +Miocene and Pliocene, not found in the Isle of Wight. +And before that there is, perhaps, an equal thickness of +sedimentary deposits; though the fossils they, no doubt, +once contained have been destroyed by changes the rocks +have undergone.</p> + +<p>Now let me try to give you some idea of the world's +<span class='pagenum'><a name="Page_72" id="Page_72">[Pg 72]</a></span> +history up to the point where we began in the Isle of +Wight. If we could see back through the ages to the +furthest past of geological history, we should see our +world,—before any of the stratified rocks were laid down +in the seas,—before the seas themselves were made,—a +hot globe, molten at least at the surface. How do we +know this? Because under the rocks of all the world's +surface we find there is granite or some similar rock,—a +rock which shows by its composition that it has crystallised +from a molten condition. Moreover we have seen +that the interior of the earth is intensely hot. And yet +all along the earth must be radiating off heat into the +cold depths of space, and cooling like any other hot body +surrounded by space cooler than itself. And this has +gone on for untold ages. Far enough back we must +come to a time when the earth was red hot,—white hot. +In imagination we see it cooling,—the molten mass solidifies +into Igneous rock,—the clouds of steam in which the +globe is wrapped condense in oceans upon the surface. +The bands of crystalline rock that rise above the primeval +seas are gradually worn down by rain and rivers and +waves, and the first sedimentary deposits laid down in +the waters. And in the waters and on the land life +appeared for the first time,—we know not how.</p> + +<p>A vast thickness of stratified rocks was formed, which +are called Archæan ("ancient"). They represent a time, +perhaps, as great as all that has followed. These rocks +have undergone great changes since their formation. +They have been pressed under masses of overlying +strata, and have come into the neighbourhood of the +heated interior of the earth; they have been burnt and +baked and compressed and folded, and acted on by heated +water and steam, and their whole structure altered by +heat and chemical action. Limestones, <i>e.g.</i>, have become +marble, with a crystalline structure which has obliterated +any fossils they may have once contained. Yet it is +<span class='pagenum'><a name="Page_73" id="Page_73">[Pg 73]</a></span> +probable that, like nearly all later limestones, they are +of organic origin. These Archæan rocks cover a large +extent of country in Canada. We have some of them in +our Islands, in the Hebrides, and north-west of Scotland +and in Anglesey, and rising from beneath later rocks in +the Malvern Hills and Charnwood Forest.<a name="FNanchor_A_12" id="FNanchor_A_12"></a><a href="#Footnote_A_12" class="fnanchor">[12]</a></p> + +<p>The Archæan rocks are succeeded by the most ancient +fossiliferous rocks, the great series called the Cambrian, +because found, and first studied, in Wales. They consist +of very hard rocks, and contain large quantities of slate. +They are followed by another series called the Ordovician; +and that by another the Silurian. These three great +systems of rocks measure in all some 30,000 ft. of strata. +They form the hills of Wales and the English Lake +District. They contain large masses of volcanic rocks. +We can see where were the necks of old volcanoes, and +the sheets of lava which flowed from them. The volcanoes +are worn down to their bases now; and the hills of Wales +and the Lakes represent the remains of ancient mountain +chains, which rose high like the Alps in days of old, long +before Alps or Himalayas began to be made. These +ancient rocks contain abundant remains of living things, +chiefly mollusca, crustaceans, corals, and other marine +organisms, showing that the waters of those ages abounded +with life.</p> + +<p>We must pass on. Next comes a period called the +Devonian, or Old Red Sandstone, when the Old Red rocks +of Devon and Scotland were laid down. These contain +remains of many varieties of very remarkable fish. A +long period of coral seas succeeded, when coral reefs +flourished over what was to be England; and their +remains formed the Carboniferous Limestone of Derbyshire +and the Mendip Hills. A period followed of +<span class='pagenum'><a name="Page_74" id="Page_74">[Pg 74]</a></span> +immense duration, when over pretty well the whole earth +there seem to have been comparatively low lands covered +with a luxuriant and very strange vegetation. The +remains of these ancient forests have formed the coal +measures, which tell of the most widespread and longest +enduring growth of vegetation the world has seen. +Strange as some of the plants were—gigantic horsetails +and club-mosses growing into trees—many were exquisitely +beautiful. There were no flowering plants, but the +ferns, many of them tree ferns, were of as delicate beauty +as those of the present day. Many of the ferns bore seeds, +and were not reproduced by spores, such as we see on the +fronds of our present ferns. That is a wonderful story +of plant history, which has only been read in recent years.</p> + +<p>After the long Carboniferous period came to an end +followed periods in which great formations of red sandstone +were made,—the Permian, and the New Red Sandstone +or Trias. During much of this time the condition +of the country seems to have resembled that of the +Steppes of Central Asia, or even the great desert of Sahara—great +dry sandy deserts—hills of bare rock with screes +of broken fragments heaped up at their base,—salt +inland lakes, depositing, as the effect of intense evaporation, +the beds of rock salt we find in Cheshire or elsewhere, in +the same manner as is taking place to-day in the Caspian +Sea, in the salt lakes of the northern edge of the Sahara, +and in the Great Salt Lake of Utah.</p> + +<p>At the close of the period the land here sank beneath +the sea—again a sea of coral islands like the South Pacific +of to-day. There were many oscillations of level, or +changes of currents; and bands of clay, when mud from +the land was laid down, alternate with beds of limestone +formed in the clearer coral seas. These strata form a +period known as the Jurassic, from the large development +of the rocks in the Jura mountains. In England the +period includes the Liassic and Oolitic epochs. The +<span class='pagenum'><a name="Page_75" id="Page_75">[Pg 75]</a></span> +Liassic strata stretch across England from Lyme Regis +in Dorset to Whitby in Yorkshire. Most of the strata +we are describing run across England from south-west to +north-east. After they were laid down a movement of +elevation, connected with the movement which raised +the Alps in Europe, took place along the lines of the +Welsh and Scotch mountains and the chain of Scandinavia, +which raised the various strata, and left them dipping to +the south-east. Worn down by denudation the edges +are now exposed in lines running south-west to north-east, +while the strata dip south-east under the edges of the +more recent strata. The Lias is noted for its ammonites, +and especially for its great marine reptiles, Ichthyosaurus +and Plesiosaurus. The Oolitic Epoch follows—a long +period during which the fine limestone, the Bath freestone, +was made; the limestones of the Cotswolds, beds of clay +known as the Oxford and Kimmeridge clays; and again +coral reefs left the rock known as coral rag. In the later +part of the period were formed the Portland and Purbeck +beds, marine and freshwater limestones, which contain +also an old land surface, which has left silicified trunks of +trees and stems of cycads.</p> + +<p>And now following on these came our Wealden strata, +the beginning of the Cretaceous period. You see what +ages and ages had gone before, and that when Wealden +times came, far back as they are, the world's history was +comparatively approaching modern times. We must +remember that all these formations, of which we have +given a rapid sketch, are of great thickness,—thousands +of feet of rock,—and represent vast ages of time. See +what we have got to from looking at the shells in the sea +cliff! We have come to learn something of the world's +old history. We have been carried back through ages +that pass our imagination to the world's beginning, to the +time of the molten globe, before ever it was cool enough +to allow life—we know not how—to begin upon its +<span class='pagenum'><a name="Page_76" id="Page_76">[Pg 76]</a></span> +surface. And Astronomy will take us back into an even +more distant past, and show us a nebulous mist of vast +extent stretching out into space like the nebulæ observed +in the heavens to-day, before sun and planets and moons +were yet formed. So we are carried into the infinite of +time and space, and questions arise beyond the power +of human mind to solve.</p> + +<p>Now we have, I hope, a better idea of the position the +strata we have been specially studying occupy in the +geological history, and shall understand the relation the +strata we may find elsewhere bear to those in the Isle +of Wight and the neighbouring south of England.</p> + +<p>After this sketch of what went before our Island story, +we must see what followed at the end of the Oligocene +period. We said that there are no strata in the British +Isles representing the next period, the Miocene. But it was +a period of great importance in the world's history. +Great stratified deposits were laid down in France and +Switzerland and elsewhere, and it was a great age of +mountain building. The Alps and the Himalaya, largely +composed of Cretaceous and Eocene rocks, were upheaved +into great mountain ranges. It is probable that during +much of the period the British Isles were dry land, and +that great denudation of the land took place. But in the +first part of the period at all events this part of the world +must have been under water, and strata have been laid +down, which have since been denuded away. For our +soft Oligocene strata, if exposed to rain and river action +during the long Miocene period and the time which followed, +would surely have been entirely swept away. The +Miocene was succeeded by the Pliocene, when the strata +called the Crag, which cover the surface of Norfolk and +Suffolk, were formed. They are marine deposits with sea +shells, of which a considerable proportion of species still +survive.</p> + +<p>We have seen that through the ages we have been +<span class='pagenum'><a name="Page_77" id="Page_77">[Pg 77]</a></span> +studying the climate was mostly warmer than at the present +day. The climate of the Eocene was tropical. The +Miocene was sub-tropical and becoming cooler. Palms +become rarer in the Upper strata. Evergreens, which +form three-fourths of the flora in the Lower Miocene, +divide the flora with deciduous trees in the Upper. And +through the Pliocene the climate, though still warmer +than now, was steadily becoming cooler; till in the +beginning of the next period, the Pleistocene, it had +become considerably colder than that of the present day. +And then followed a time which is known as the great +Ice Age, or the Glacial Period,—a time which has left its +traces all over this country, and, indeed all over Northern +Europe and America, and even into southern lands. The +cold increased, heavy snowfalls piled up snow on the +mountains of Wales, the Lake District, and Scotland; +and the snow remained, and did not melt, and more fell +and pressed the lower snow into ice, which flowed down +the valleys in glaciers, as in Switzerland to-day. Gradually +all the vegetation of temperate lands disappeared, till +only the dwarf Arctic birch and Arctic willows were to be +seen. The sea shells of temperate climates were replaced +by northern species. Animals of warm and temperate +climates wandered south, and the Arctic fox, and the +Norwegian lemming, and the musk ox which now lives in +the far north of America took their place; and the +mammoth, an extinct elephant fitted by a thick coat of +hair and wool for living in cold countries, and a woolly-haired +rhinoceros, and other animals of arctic regions +occupied the land. When the cold was greatest, the +glaciers met and formed an ice-sheet; and Scotland, +northern England and the Midlands, Wales, and Ireland +were buried in one vast sheet of ice as Greenland is to-day.</p> + +<p>How do we know this? To tell how the story has been +read would be to tell one of the most interesting stories +of geology. Here we can only give the briefest sketch of +<span class='pagenum'><a name="Page_78" id="Page_78">[Pg 78]</a></span> +this wonderful chapter of the world's history. But we +must know a little of how the story has been made out. +We have already seen that the changes in plant and +animal life point to a change from a hot climate, through +a temperate, at last to arctic cold. Again, over the +greater part of Northern England the rocks of the various +geological periods are buried under sheets of tough clay, +called boulder clay, for it is studded with boulders large +and small, like raisins in a plum pudding. No flowing +water forms such a deposit, but it is found to be just like +the mass of clay with stones under the great glaciers and +ice sheets of arctic regions; and just such a boulder clay +may be seen extending from the lower end of glaciers in +Spitzbergen, when the glacier has temporarily retreated +in a succession of warm summers. The stones in our +boulder clay are polished and scratched in a way glaciers +are known to polish and scratch the stones they carry +along, and rub against the rocks and other stones. The +rock over which the glacier moves is similarly scratched +and polished, and just such scratching and polishing is +found on the rocks in Wales and the Lake District. +Again, we find rocks carried over hill and dale and right +across valleys, it may be half across England. We can +trace for great distances the lines of fragments of some +peculiar rock, as the granite of Shap in Westmorland; and +even rocks from Norway have been carried across the North +Sea, and left in East Anglia. This will just give an idea how +we know of this strange chapter in the history of our land. +For, by this time it was our land—England—much as we +know it to-day; though at times the whole stood higher +above sea level, so that the beds of the Channel and the +North Sea were dry land. But, apart from variation of +level, the geography was in the main as now.</p> +<p> </p> +<p> </p> + +<a name="Fig_9" id="Fig_9"></a> +<div class="text_rt smcap">Fig. 9</div> +<div class="center"> + <img src="images/fig_9.png" width="340" height="74" border="0" title="SHINGLE AT FORELAND." alt="SHINGLE AT FORELAND." /><br> + <table class="smaller" summary="Fig_9 Caption"> + <tr><td colspan=5 class="center">SHINGLE AT FORELAND.</td></tr> + <tr><td colspan=5 class="center"> </td></tr> <tr><td>Bm</td><td><i>Bembridge Marls.</i></td><td> </td><td>b</td><td><i>Brick Earth.</i></td> + <tr><td>S</td><td><i>Shingle.</i></td><td> </td><td>Cf</td><td><i>Old Cliff in Marls.</i></td> +</table></div> +<p> </p> + +<a name="Fig_5" id="Fig_5"></a> +<div class="text_rt smcap">Fig. 5</div> +<div class="center"> + <img src="images/fig_5.png" width="471" height="140" border="0" title="DIAGRAM OF STRATA BETWEEN SOUTHERN DOWNS AND ST. GEORGE'S DOWN." alt="DIAGRAM OF STRATA BETWEEN SOUTHERN DOWNS AND ST. GEORGE'S DOWN." /><br> + <table class="smaller"summary="Fig. Caption"> + <tr><td>Dotted Lines</td><td><i>Former extension of Strata.</i></td></tr> + <tr><td>Broken Line</td><td><i>Former Bed of Valley sloping to St. George's Down.</i></td></tr> + </table> +</div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_79" id="Page_79">[Pg 79]</a></span> +The ice sheet did not come further south than the +Thames valley. What was the country like south of +this? Well, you must think of the land just outside the +ice sheet in Greenland, or other arctic country. No +doubt the winters must have been very severe,—hard +frosts and heavy snows,—the ground frozen deep. Some +arctic animals would manage to live as they do now just +outside the ice sheet in Greenland. Now, have we any +deposits formed at that time in the Isle of Wight? I +think we have. A large part of the surface of the Island +is covered by sheets of flint gravel. The gravels differ +in age and mode of formation. We have already considered +the angular gravels of the Chalk downs, composed +of flints which have accumulated as the chalk which +once contained them was dissolved away. But there are +other gravel beds, which consist of flints which, after they +were set free by the dissolution of the chalk, have been +carried down to a lower level by rivers or other agency, +and more or less rounded in the process. Many of these +beds occur at a high level; and, as they usually cap flat-topped +hills, they are known as Plateau Gravels. Perhaps +the most remarkable is the immense sheet of gravel +which covers the flat top of St. George's Down between +Arreton and Newport. Gravel pits show upwards of +30 feet of gravel, consisting of flints with some chert and +ironstone, and the greatest thickness is probably considerably +more than this. The southern edge of the +sheet is cut off straight like a wall. To the north it runs +out on ridges between combes which have cut into it. In +places in the mass of flints occur beds of sand, which have +all the appearance of having been laid down by currents +of water. The base of the gravel where it is seen on the +steep southern slope of the down has been cemented by +water containing iron into a solid conglomerate rock. +The flints forming this gravel have not simply sunk down +from chalk strata dissolved away; for they lie on the +upturned edges of strata from Lower Greensand to Upper +Chalk, which have been planed off, and worn into a +surface sloping gently to the north; and over this surface +<span class='pagenum'><a name="Page_80" id="Page_80">[Pg 80]</a></span> +the gravel has somehow flowed. The sharp wall in which +it ends at the upper part of the slope shows that it once +extended to the south over ground since worn away. +Clearly, the gravel was formed before denudation had cut +out the great gap between the central and southern downs +of the Island. The down where the gravel lies is 363 ft. +above sea level, 313 ft. above the bottom of the valley +below. So that, though the gravel sheet is much newer +than the strata we have been studying, it must nevertheless +be of great antiquity.</p> + +<p>It seems that at the top of St. George's Down we are +standing on what was once the floor of an old valley. In +the course of denudation the bottom of a river valley +often becomes the highest part of a district. For the bed +of the valley is covered by flint gravel, and flint is excessively +hard, and the bed of flints protects the underlying +rock; so that, while the rocks on each side are worn +away, what was the river bed is eventually left high +above them. Thus the highest points of a district are +often capped by flint gravel marking the beds of old +streams. Tracing up this old valley to the southward, +at a few miles distance it will have reached the chalk +region on the south of the anticline: and the flints carried +down the valley may have come from beds of angular +flints already dissolved out of the chalk such as we find +on St. Boniface Down.</p> + +<p>But how have these great masses of flints been swept +along? Can the land have been down under the sea; +and have sea waves washed the stones along? But these +flints, though water-worn, are not rounded as we find +beach shingle. What immense rush of water can have +spread these flints 30 feet deep along a river valley? +We must go to mountain regions for torrents of this +character. And then, mountain torrents round the stones +in their bed while these are mostly angular. The history +of these gravels is a difficult one. I can only give what +<span class='pagenum'><a name="Page_81" id="Page_81">[Pg 81]</a></span> +seems to me the most probable explanation. It appears +to me probable that in the Ice Age, south of the ice sheet, +the ground must have been both broken up by frosts, and +also held together by being frozen hard to some depth. +Then when thaws came in the short but warm summers, +or when an intermission of the severe cold took place, +great floods would flow down the valleys in the country +south of the ice sheet, and masses of ice with frozen earth +and stones would be borne along in a sort of semi-liquid +flow. In this way Mr. Clement Reid explains the mass +of broken-up chalk with large stones found on the heads +of cliffs on the South coast, and known by the name of +"combe-rock" or "head."</p> + +<p>The Ice Age was not one simple period, and it is still +difficult to fit together the history we read in different +places, and in particular to correlate the gravels of the +south of England with the boulder clays of the glaciated +area. There were certainly breaks in the period, during +which the climate became much milder, or even warm; +and these were long enough for southern species of +animals and plants to migrate northward, and occupy the +lands where an arctic climate had prevailed. There were +moreover considerable variations in the relative level of +land and sea. So that we have a very complex history, +which is gradually coming into clearer light.</p> + +<p>That the gravels of the south of England belong largely +to the age of ice, is shown by remains of the mammoth +contained in many. These, however, are found in later +gravels than those we have considered so far, gravels laid +down after the land had been cut down to much lower +levels. These lower gravels are known as Valley gravels, +because they lie along the course of existing valleys, the +Plateau gravels having been laid down before the present +valleys came into existence. Teeth of the mammoth +are found in the Thames valley, and on the shores of +Southampton Water, in gravels about 50 to 70 feet above +<span class='pagenum'><a name="Page_82" id="Page_82">[Pg 82]</a></span> +sea level, and have been found also in the Isle of Wight +at Freshwater Gate, at the top of the cliffs near Brook, +and in other places. The gravels near Brook with the +clays on which they rest have been contorted, and the +gravel forced into pockets in the clay, in a manner that +suggests the action of grounding ice ploughing into the soil.</p> + +<p>The high level gravels must belong to an early stage of +the Glacial Epoch. We get some idea of the great length +of time this age must have lasted, as we look from St. +George's Down over the lower country of the centre of +the Island. After the formation of the St. George's Down +gravel the vast mass of strata between this and the opposite +downs of St. Boniface and St. Catherine's was removed by +denudation; and gravels were then laid down on the +lower land, along Blake Down, at Arreton, over Hale +common, and along the course of the Yar. Patches of +gravel occur on the Sandown and Shanklin cliffs. At +Little Stairs a gravel, largely of angular chert, reaches a +thickness of 12 feet, and in parts are several feet of loam +above gravel.</p> + +<p>At the west of the Island a great sheet of gravel covers +the top of Headon Hill, reaching a height of 390 feet. It +appears sometimes to measure 30 feet in thickness. Like +that on St. George's Down it slopes towards the Solent, +resting on an eroded surface, in this case of Tertiary +strata; and here too the upper part of the sheet has been +removed by the wearing out of the deep valley between +the Hill and the Freshwater Downs. The sheet lies on +an old valley bottom, which sloped from the chalk downs +on the south, then much higher and more extensive than +now. Here too we may see something of the length of +the Glacial Period. For at Freshwater Gate is a much +later gravel, in which teeth of the mammoth have been +found. It was probably derived from older gravels that +once lay to the south, as the flints are rounded by transport. +But the formation of all these gravels appears to +<span class='pagenum'><a name="Page_83" id="Page_83">[Pg 83]</a></span> +belong to the Glacial Period; and as we stand in Freshwater +Gate, and look at this great gap in the downs worn +out by the Western Yar, and think of the time when a +river valley passed over the tops of the High Downs and +Headon Hill, we receive a strong impression of the length +of the great Ice Age.</p> + +<p>Now surely the question will be asked, what caused +these changes of climate in the world's past history—so +that at times a tropical vegetation spread over this land, +and vegetation flourished sufficient to leave beds of coal +within the Arctic circle, and in the Antarctic continent, +and at another the climate of Greenland came down to +England, and an ice sheet covered nearly the whole +country? This still remains one of the difficult problems +of Geology. An explanation has been attempted by +Astronomical Theory, according to which the varying +eccentricity of the earth's orbit—that is to say a slight +change in the elliptic orbit of the Earth, by which at times +it becomes less nearly circular—a change which is known +to take place—may have had the effect of producing these +variations of climatic conditions. The theory is very +alluring, for if this be the cause, we can calculate mathematically +the date and duration of the Glacial Period. +But, unfortunately, supposing the astronomical phenomena +to have the effect required, the course of events +given by the astronomical theory would be entirely different +to that revealed by geological research. Geographical +explanations have usually failed through being +of too local a character to explain a phenomenon which +affected the whole northern hemisphere, and the effects +of which reached at least as far south as the Equator,<a name="FNanchor_A_13" id="FNanchor_A_13"></a><a href="#Footnote_A_13" class="fnanchor">[13]</a> +and are seen again in the southern hemisphere in Australia, +New Zealand, and South America. It is now +believed that great world-movements take place, due to +<span class='pagenum'><a name="Page_84" id="Page_84">[Pg 84]</a></span> +the contraction by cooling of the Earth's interior, and +the adjustment of the crust to the shrinkage.<a name="FNanchor_A_14" id="FNanchor_A_14"></a><a href="#Footnote_A_14" class="fnanchor">[14]</a> Possibly +some explanation might be found in these world-wide +movements; but their effect seems to last through too +long periods of time to suit our Ice Ages. Again, while +the geographical distribution of animals and plants in +the present and past seems to imply very great changes +in the land masses and oceanic areas,<a name="FNanchor_B_15" id="FNanchor_B_15"></a><a href="#Footnote_B_15" class="fnanchor">[15]</a> these changes +appear to bear no relation to glacial epochs. The cause +of the Ice Ages remains at present an unsolved problem. +More than one Ice Age has occurred during the long +geological history. The marks of such a period are found +in Archæan rocks, in the Cambrian, when glaciers flowed +down to the sea level in China and South Australia within +a few degrees of the tropics, and above all in early Permian +times. The Dwyka conglomerate of the Karroo +formation of South Africa (deposits of Permo-Carboniferous +age) show evidence of extensive glaciation; deposits +of the same age in Northern and Central India, +even within the tropics, a glacial series of great thickness +in Australia, and deposits in Brazil, appear to show a +glaciation greater than that of the recent glacial period. +Yet these epochs formed only episodes in the great +geological eras. On the whole the climate throughout +geological time would seem to have been warmer than at +the present day. It may, perhaps, be doubted whether +the earth has yet recovered what we may call its <i>normal</i> +temperature since the Glacial Epoch.</p> + +<p>Note on Astronomical Theory.—If the Ice Age be due +to the increased eccentricity of the Earth's orbit, the +theory shows that a long duration of normal temperature +<span class='pagenum'><a name="Page_85" id="Page_85">[Pg 85]</a></span> +will be followed by a group of Glacial Periods alternating +between the northern and southern hemispheres, the time +elapsing between the culmination of such a period in one +hemisphere and in the other being about 10,500 years. +While one hemisphere is in a glacial period, the other will +be enjoying a specially mild,—a "genial" period. Now, +according to the record of the rocks, the "genial" periods +were far from being those breaks in the Glacial which we +know as Inter-glacial periods. We have the immensely +long warm period of the Eocene and Oligocene, the +Miocene with a still warm but reduced temperature, and +then the gradual cooling during the Pliocene, till the +drop in temperature culminates in the Ice Age. Moreover, +the duration of each glaciation during this Ice Age +is usually considered to have been much longer than the +10,000 years or so given by the Astronomical Theory. +Add to this that the periods of high eccentricity of the +Earth's orbit, though occurring at irregular intervals, are, +on the scale of geological time, pretty frequent; so that +several of such periods would have occurred during the +Eocene alone. Yet the geological evidence shows unbroken +sub-tropical conditions in this part of the world +throughout the Eocene.</p> + +<div class="footnote"><p><a name="Footnote_A_12" id="Footnote_A_12"></a><a href="#FNanchor_A_12"><span class="label">[12]</span></a> The older division of the Archæan rocks—the Lewisian +gneisse—consists entirely of metamorphic and igneous rocks; a +later division—the Torridonian sandstones—is comparatively little +altered, but still unfossiliferous.</p></div> + +<div class="footnote"><p><a name="Footnote_A_13" id="Footnote_A_13"></a><a href="#FNanchor_A_13"><span class="label">[13]</span></a> The great equatorial mountains Kilimanjaro and Ruwenzori +show signs of a former extension of glaciers.</p></div> + +<div class="footnote"><p><a name="Footnote_A_14" id="Footnote_A_14"></a><a href="#FNanchor_A_14"><span class="label">[14]</span></a> For an account of such movements, see Prof. Gregory's <i>Making +of the Earth</i> in the Home University Library.</p></div> + +<div class="footnote"><p><a name="Footnote_B_15" id="Footnote_B_15"></a><a href="#FNanchor_B_15"><span class="label">[15]</span></a> See The <i>Wanderings of Animals</i>. By H. Gadow, F.R.S., Cambridge +Manuals.</p></div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_86" id="Page_86">[Pg 86]</a></span></p> + +<div class="chapt_hdr">Chapter XI</div> +<div class="chapt_ttl">THE STORY OF THE ISLAND RIVERS; AND HOW +THE ISLE OF WIGHT BECAME AN ISLAND</div> + +<p>We must now consider the history of the river system of +the Isle of Wight, to which our study of the gravels has +brought us. For rivers have a history, sometimes a most +interesting one, which carries us back far into the past. +Even the little rivers of the Isle of Wight may be truly +called ancient rivers. For though recent in comparison +with the ages of geological time, they are of a vast antiquity +compared with the historical periods of human +history.</p> + +<p>To understand our river systems we must go back to +the time when strata formed by deposit of sediment in +the sea were upheaved above the sea level. To take the +simplest case, that of a single anticlinal axis fading off +gradually at each end, we shall have a sort of turtle back +of land emerged from the sea, as in <a href="#Fig_6">figure 6, <i>aa</i></a> being +the anticlinal axis. From this ridge streams will run +down on either side in the direction of the dip, their course +being determined by some minor folds of the strata, or +difference of hardness in the surface, or cracks formed +during elevation. On each side of the dip-streams smaller +ones will flow, more or less in the direction of the strike, +and run into the main streams. Various irregularities, +such as started the flow of the streams, will favour one or +another. Consider three streams, <i>a</i>, <i>b</i>, <i>c</i>, and let us suppose +the middle one the strongest, with greatest flow of +water, and cutting down its bed most rapidly. Its side +streams will become steeper and have more erosive force, +and so will eat back their courses most rapidly until they +strike the line of the streams on either side. Their steeper +channels will then offer the best way for the upper waters +of the streams they have cut to reach the sea; and these +streams will consequently be tapped, and their head +waters cut off to flow to the channel of the centre stream. +We shall thus have for a second stage in the history a +system such as is shown in <a href="#Fig_7">fig. 7</a>. The same process will +continue till one river has tapped several others; and +there will result the usual figure of a river and its +tributaries, to which we are accustomed on our maps. +We shall observe that tributaries do not as a rule gradually +approach the central stream, but suddenly turn off at +nearly a right angle from the direction in which they are +flowing, and, after a longer or shorter course, join at +another sharp angle a river flowing more or less parallel +to their original direction.</p> +<p> </p> +<p> </p> + +<a name="Fig_6" id="Fig_6"></a> +<div class="text_rt smcap">Fig. 6</div> +<div class="center"> + <img src="images/fig_6.png" width="500" height="238" title="" alt="" /> +<p> </p> + +<a name="Fig_7" id="Fig_7"></a> +<div class="text_rt smcap">Fig. 7</div> + <img src="images/fig_7.png" width="600" height="433" title="" alt="" /> +<p> </p> + +<div class="caption3">Development Of River Systems</div> +</div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_125" id="Page_125">[Pg 125]</a></span> +The Chalk and overlying Tertiary strata were uplifted +from the sea in great folds forming a series of such turtle-backs +as we have been considering. The line of upheaval +was not south-west and north-east, as that which raised +the older formations in bands across England, but took +place in an east and west direction. The main upheaval +was that of the great Wealden anticline. Other folds +produced the Sandown and Brook anticlines, and that +of the Portsdown Hills. The upheaval seemed to have +been caused by pressure acting from the south, for the +steeper slope of each fold is on the northern side. Our +latest Oligocene strata are tilted with the chalk, showing +that the upheaval took place after Oligocene times. But +the great movement was in the main earlier than the +Pliocene. For on the North Downs near Lenham is a +patch of Lower Pliocene deposit resting directly on the +Chalk, the older Tertiary strata having been removed by +denudation, clearly due to the uplift of the Wealden +anticline. The raising of the Pliocene deposit to its +<span class='pagenum'><a name="Page_88" id="Page_88">[Pg 88]</a></span> +present position proves that the same movement was continued +at a later time, probably during the Pleistocene. +But the greater part of the movement may be assigned to +the Miocene, the period of great world-movements which +raised the Alps and the Himalaya.</p> + +<p>Many remarkable, and, at first sight, very puzzling +features connected with the courses of rivers find an +explanation when we study the river history. Thus, +looking at the Weald of Kent and Sussex, we see that it +consists of comparatively low ground rising to a line of +heights east and west along the centre, and surrounded +on all sides but the south-east by a wall of Chalk downs. +If we considered the subject, we should suppose that the +drainage of the country would be towards the south-east, +which is open to the sea. Not so. All the rivers flow from +the central heights north and south,—go straight for the +walls of chalk downs, and cut through the escarpment in +deep clefts to flow into the Thames and the Channel. +This is explained when we remember that the rivers began +to flow when the great curve of strata rose above the sea. +Though eroded by the sea during its elevation, yet when +it rose above the waters the arch of chalk must have been +continuous from what are now North Downs to South. +And from the centre line of the great turtle back the +streams began to flow north and south, cutting in the +course of ages deep channels for themselves. The greater +erosion in their higher courses has cut away the mass of +chalk from the centre of the Weald, but the rivers still +flow in the direction determined when the arch was still +entire.</p> + +<p>We have a similar state of things in the Isle of Wight. +Any one not knowing the geological story, and looking at +the geography of the Island, might naturally suppose +that there would be a stream flowing from west to east, +through the low ground between the two ranges of downs, +and finding its way into the sea in Sandown Bay. Instead +<span class='pagenum'><a name="Page_89" id="Page_89">[Pg 89]</a></span> +of this the three rivers of the Island, the two Yars and the +Medina, all flow north, and cut through the chalk escarpment +of the Central downs, as if an earthquake had made +rifts for them to pass, and so find their way into the +Solent. The explanation is the same as in the case of the +Weald. The rivers began to flow when the Chalk strata +were continuous over the centre of the Island; and their +course was determined when the east and west anticlinal +axis rose above the sea.</p> + +<p>We shall notice, however, that the Island rivers start +from south of the anticlinal axis. The centre of the +Sandown anticline runs just north of Sandown, but the +various branches of the Yar and Medina flow from well +south of this. The explanation would appear to be that +the anticline is almost a monoclinal curve,—that is to say, +one slope is steep, the other not far from horizontal. +Streams starting from the ridge would flow with much +greater force down the northern than the southern side, +and would cut back their course much more quickly. +Thus they would continually cut into the heads of the +southern streams, and turn the water supplying them +into their own channels.</p> + +<p>In its early history a river cuts out its bed, and carries +along pebbles, sand and mud to the sea. The head waters +are constantly cutting back, and the slope becoming less +steep, till a time comes when the stream in its gently +inclined lower course has no more power to excavate, +and the finer sediment, which is all that now reaches the +lower river, begins to fill up the old channel. And so the +alluvium is formed which fills the lower portions of our +river valleys.</p> + +<p>Beyond this, the great rush of waters from melting +snows and ice of the Glacial Period has come to an end. +The gentler and diminished streams of a drier age have +no power to roll flint stones along and form beds of gravel. +Gravel terraces border our river valleys at a higher +<span class='pagenum'><a name="Page_90" id="Page_90">[Pg 90]</a></span> +level than the present streams. Periods alternated during +which gravels were laid down by the river, and when the +river acquiring more erosive force, by an elevation of the +land giving its bed a steeper gradient, or a wetter climate +producing a greater rush of water, cut a new channel +deeper in the old valley. So our valleys in Southern +England are frequently bordered by a succession of gravel +terraces, the higher ones being the older, dating from times +when the river flowed at a higher level than at present. +Such terraces may be seen above the Eastern Yar and its +tributary streams. In the centre of the old gravels is the +alluvial flat of a later age.</p> + +<p>The Island rivers cut out their channels when the land +stood at a higher level than at present. The old channels +of the lower parts of the rivers are now filled with alluvium, +partly brought down by the rivers and partly marine. +The channels are cut down considerably below sea level; +and by the sinking of the land the sea has flowed in, and +the last parts of the river courses are now tidal estuaries. +The sea does not cut out estuaries. They are the submerged +ends of river valleys.</p> + +<p>Some idea may be formed of the antiquity of our Island +rivers by observing the depth of the clefts they have cut +through the downs at Brading, Newport, and Freshwater. +But to this we must add the depth at which the old +channels lie below the alluvium. It would be interesting +to know the thickness of the alluvium. But it is not often +that borings come to be made in river alluvia. However, +in the old Spithead forts artesian wells are sunk; and +these pass through 70 to 90 feet of recent deposits before +entering Eocene strata. Under St. Helen's Fort, at the +mouth of Brading Harbour, are 80 feet of recent deposits. +The old channel of the Yar, at its mouth, must lie at least +at this depth.</p> + +<p>Before it passes through the gap in the Chalk downs +the Yar has meandered about, and formed the alluvial +<span class='pagenum'><a name="Page_91" id="Page_91">[Pg 91]</a></span> +flat called Morton marshes. These marshes stretch out +into the flat known as Sandown Level, which occupies the +shore of the bay between Sandown and the Granite Fort. +What is the meaning of this extension of the alluvium +away from the course of the river out to the sea at Sandown? +A glance at it as pictured on a geological map +will suggest the answer. We see clearly the alluvia of +two streams converging from right and left, and uniting +to pass to the sea through Brading Harbour. But the +stream to the right has been cut off by the sea encroaching +on Sandown Bay: only the last mile of alluvium is left +to tell of a river passed away. We must reconstruct the +past. We see the Bay covered by land sloping up to east +and south east, the lines of downs extending eastward +from Dunnose and the Culvers, and an old river flowing +northward, and cutting through the chalk at Brading +after being joined by a branch from the west. This old +river must have been the main stream. For it was a +transverse stream, flowing nearly at right angles to the +ridge of the anticline; while the Yar comes in as a tributary +in the direction of the strike. Of other tributary +streams, all from the right are gone by the destruction of +the old land. On the left streams would flow in from the +combes at Shanklin and Luccombe—streams which have +now cut out Shanklin and Luccombe chines.</p> + +<p>Passing the gap in the downs the river meandered about, +and, with marine deposit, washed in by the tides, formed +the expanse of alluvium which occupies what was Brading +Harbour,—a harbour which in old times presented at high +tide a beautiful spectacle of land-locked water extending +up to Brading. Inclosures and drainings have been made +from time to time, the upper part near Yarbridge being +taken in in the time of Edward I. Further innings were +made in the reign of Queen Elizabeth; and Sir Hugh +Middleton, who brought the New River to London, +made an attempt to enclose the whole, but the sea broke +<span class='pagenum'><a name="Page_92" id="Page_92">[Pg 92]</a></span> +through his embankment. The harbour was finally +reclaimed at great cost in 1880, the present embankment +enclosing an area of 600 acres.</p> + +<p>The history of the Western Yar is similar to that of the +Eastern. The main stream must have flowed from land +now destroyed by the sea stretching far south of Freshwater +Gate. All that is left is its tidal estuary, and the +gravel terraces and alluvial flat formed in the last part of +its course. Of a tributary stream an interesting relic +remains. For more than 2 miles from Chilton Chine +through Brook to Compton Grange a bed of river gravel +lies at the top of the cliff, marking the course of an old +stream, of which coast erosion has made a longitudinal +section. This was a tributary of the Yar, when the +mammoth left his remains in the gravel at Grange Chine +and Freshwater Gate. Down the centre of the gravels +lies a strip of alluvium laid down by a stream following +the same course in later days. The sea had probably by +this time cut into the stream; and it most likely flowed +into the sea somewhere west of Brook. In the alluvium +hazel nuts and twigs of trees are found at Shippard's +Chine near Brook.</p> + +<p>The lower course of the Medina is a submerged river +valley, the tide flowing up to Newport. The river rises +near Chale, and flows through a strip of alluvium, overgrown +with marsh vegetation, known as "The Wilderness." +This upper course of the Medina, from the absence +of gravels or brick earth, has the appearance of a comparatively +modern river. But the Medina has a further +history. If you look at the map you will see branches +of the Yar running south to north as transverse streams, +but the main course is that of a lateral river. Look at +the two chief sources of the Yar—the stream from near +Whitwell and Niton, and that from the Wroxall valley. +When they get down to the marshes near Rookley and +Merston, they are not flowing at all in the direction of +<span class='pagenum'><a name="Page_93" id="Page_93">[Pg 93]</a></span> +Sandown or Brading. They rather look as if they would +flow along the marshy flat by Blackwater into the Medina. +But the Yar cuts right across their course, and carries +them off eastward to Sandown. When we look, we find +a line of river valley with a strip of alluvium running up +from the Medina at Blackwater in the direction of these +two streams—a valley which the railway up the Yar +valley from Sandown makes use of to get to Newport. +There can be little doubt that these streams from Niton +and Wroxall originally ran along this line into the +Medina; but the Yar, cutting its course backward, has +captured them, and diverted their course. They probably +represent the main branches of the Medina in earlier +times, the direction of flow from south-east to north-west +instead of south to north being possibly due to the overlapping +in the neighbourhood of Newport of the ends of +the Brook and Sandown anticlines. The sheet of gravel +on Blake Down belongs to this period of the river's history. +The river must have diverted between the deposition of +the Plateau Gravels and that of the Valley Gravels of the +Yar. For the former follow the original valley, the +latter the new course of the river.</p> + +<p>We must now take a wider outlook, and see what became +of our rivers after they had flowed across what is now the +Isle of Wight from south to north. We have been speaking +of times when the Island was of much greater extent +than at present. Standing on the down above the Needles, +and looking westward, we see on a clear day the Isle of +Purbeck lying opposite, and we can see that the headland +there is formed by white chalk cliffs like those beneath us. +In front of them stand the Old Harry Rocks, answering to +the Needles, both relics of a former extension of the land. +In fact Purbeck is just like a continuation of the Isle of +Wight. South of the Chalk lie Greensand and Wealden +strata in Swanage Bay, and north towards Poole are +Tertiaries. Clearly these strata were once continuous +<span class='pagenum'><a name="Page_94" id="Page_94">[Pg 94]</a></span> +with those of the Isle of Wight. We must imagine +the chalk downs of the Island continued as a long range +across what is now sea, and on through Purbeck. A great +Valley must have stretched from west to east, north of +this line, along the course of the Frome, which runs +through Dorset, and now enters the sea at Poole Harbour, +on by Bournemouth, and along the present Solent Channel—a +valley still much above sea level, not yet cut down by +rivers and the sea—and down the centre of this valley a +river must have flowed, which may be called the River +Solent. It received as tributaries from the south the +rivers of the Isle of Wight, and others from land since +destroyed by the sea. There flowed into it from the +north the waters of the Stour and Avon, and an old river +which flowed down the line of what is now Southampton +Water. Southampton Water looks like the valley of a +large river, much larger than the present Test and Itchen. +Its direction points to a river from the north west; and +it has been shown by Mr. Clement Reid that the Salisbury +rivers—Avon, Nadder, and Wily—at a former time, when +they flowed far above their present level—continued their +course into the valley of Southampton Water. For fragments +of Purbeck rocks from the Vale of Wardour, west +of Salisbury, have been found by him in gravels on high +land near Bramshaw, carried right over the deep vale of +the Avon in the direction of the Water. The lower Avon +would originally be a tributary of the Solent River; and +it enters the sea about mid-way between the Needles +and the chalk cliffs of Purbeck, just opposite the point +where we might suppose the sea would have first broken +through the line of chalk downs. No doubt it broke +through a gap made by the course of an old river from the +south, as it is now breaking through the gap made by the +old Yar at Freshwater. When the river Solent had been +tapped at this point, the Avon just opposite would have +acquired a much steeper flow, causing it to cut back at a +faster rate, till it cut the course of the old river which ran +by Salisbury to Southampton, and, having a steeper fall, +diverted the upper waters of this river into its own +channel.</p> +<p> </p> +<p> </p> + +<a name="Fig_8" id="Fig_8"></a> +<div class="smcap text_rt">Fig 8</div> + +<div class="center"> + <img src="images/fig_8.png" width="600" height="421" title="The Old Solent River" alt="The Old Solent River" /> +</div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_95" id="Page_95">[Pg 95]</a></span> +Frost and rain and rivers cut down the valleys of the +river system for hundreds of feet; the sea which had +broken through the chalk range gradually cut away the +south side of the main river valley from Purbeck to the +Needles; and eventually the valley itself was submerged +by a subsidence of the land, and the sea flowed between +the Isle of Wight and the mainland.</p> + +<p>A gravel of somewhat different character to the rest is +the sheet of flint shingle at Bembridge Foreland. It +forms a cliff of gravel about 25 feet high resting on +Bembridge marls, and consists of large flints, with lines of +smaller flints and sand showing current bedding, and also +contains Greensand chert and sandstone, which must +have been brought from some district beyond the Chalk. +The shingle slopes to north-east. To the south-west it +ends abruptly, the dividing line between shingle and marls +running up steeply into the cliff. This evidently marks +an old sea cliff in the marls, against which the gravel has +been laid down.<a name="FNanchor_A_16" id="FNanchor_A_16"></a><a href="#Footnote_A_16" class="fnanchor">[16]</a></p> + +<p>One or two comparatively recent deposits may be +mentioned here. At the top of the cliff in Totland Bay, +about 60 ft. above the sea, for a distance of 350 yards, is a +lacustrine deposit, consisting in the main of a calcareous +tufa deposited by springs flowing from the limestone of +Headon Hill. The tufa contains black lines from vegetable +matter, and numerous land and freshwater shells +of present-day species—many species of Helix, especially +<i>H. nemoralis</i> and <i>H. rotundata</i>, <i>Cyclostoma elegans</i>, <i>Limnæa +palustris</i>, <i>Pupa</i>, <i>Clausilia</i>, <i>Cyclas</i>, and others.</p> + +<p>On the top of Gore Cliff is a deposit of hard calcareous +mud, reaching a thickness of about 9 feet, and forming a +small vertical cliff above the slopes of chalk marl. It +extends north a few yards beyond the chalk marl on to +Lower Greensand. It has been formed by rainwash from +a hill of chalk, which must once have existed to the south. +The deposit contains numerous existing land-shells, +especially <i>Helix nemoralis</i> and other species of Helix.</p> + +<p><span class='pagenum'><a name="Page_96" id="Page_96">[Pg 96]</a></span> +Between Atherfield and Chale at the top of the cliff is +a large area of Blown Sand. The sand is blown up from +the face of the cliff below. It reaches a thickness of 20 +feet, and possibly more in places, and forms a line of +sand dunes along the edge of the cliff. The upper part of +Ladder Chine shows an interesting example of wind-erosion. +The sand driven round it by the wind has worn +it into a semi-circular hollow like a Roman theatre.</p> + +<p>Small spits, consisting partly of blown sand, extend +opposite the mouths of the Western Yar, the Newtown +river, and the most extensive—at the mouth of the old +Brading Harbour, separating the present reduced Bembridge +Harbour from the sea. This is called St. Helen's +Spit, or "Dover,"—the local name for these sand spits.</p> + +<div class="footnote"><p><a name="Footnote_A_16" id="Footnote_A_16"></a><a href="#FNanchor_A_16"><span class="label">[16]</span></a> <a href="#Fig_9">Fig. 9</a>, <a href="#Page_79">p. 79</a>.</p></div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_97" id="Page_97">[Pg 97]</a></span></p> + +<div class="chapt_hdr">Chapter XII</div> +<div class="chapt_ttl">THE COMING OF MAN.</div> + +<p>We have watched the long succession of varied life on the +earth recorded in the rocks, and now we come to the most +momentous event of all in the history—the coming of Man. +The first certain evidence of the presence of man on the +earth is found with the coming of the Glacial Period,—unless +indeed the supposed flint implements found by +Mr. Reid Moir, under the Crag in Suffolk, should prove him +earlier still. It is a rare chance that the skeleton of a land +animal is preserved; especially rare in the case of a skeleton +so frail as that of man. The best chance for the preservation +of bones is in deposits in caves, which were frequently +the dens of wild beasts and the shelters of man. But the +implements used by early man were happily of a very +imperishable nature. His favourite material, if he could +get it, was flint. Flint could by dexterous blows have +flake after flake taken off, till it formed a tool or weapon +with sharp point and cutting edge. The implements, +though only chipped, or flaked, were often admirably +made. They have very characteristic shapes. Moreover, +the kind of blow—struck obliquely—by which these early +men made their tools left marks which stamp them as of +human workmanship. The flake struck off shows what is +called a "bulb of percussion"—a swelling which marks +the spot where the blow was struck—and from this +extends a series of ripples, producing a surface like that of a +shell, from which this mode of breaking is called conchoidal +fracture. Often, by further chipping the flake itself is +worked into an implement. Implements have also been +<span class='pagenum'><a name="Page_98" id="Page_98">[Pg 98]</a></span> +made of chert, but it is far more difficult to work, as it +naturally breaks in an irregular way into sharp angular +fragments. Flint, on the other hand, lent itself admirably +to the use of early man, who in time acquired a perfect +mastery of the material. The working of flints is so +characteristic that, once accustomed to them, you cannot +mistake a good specimen. Sea waves dashing pebbles +about will sometimes produce a conchoidal fracture, but +never a series of fractures in the methodical way in which +a flint was worked by man. And, of course, specimens +may be found so worn that it is difficult to be sure about +their nature. Again early man may, especially in very +early times, have been content to use a sharp stone almost +as he found it, with only the slightest amount of knocking +it into shape. So that in such a case it will be very +difficult to decide whether the stones have formed the +implements of man or not. In later times men learnt to +polish their implements, and made polished stone axes +like those the New Zealanders and South Sea Islanders +used to make in modern times. The old age of chipped or +flaked implements is called the Palæolithic; the later age +when they were ground or polished the Neolithic. (Simple +implements, as knives and scrapers, were still unpolished.) +The history of early man is a long story in itself, and of +intense interest. But we must not leave our geological +story unfinished by leaving out the culmination of it all +in man. In the higher gravels—the Plateau Gravels—no +remains of man are found; but in the lower—the +Valley Gravels,—of the South of England is found abundant +evidence of the presence of man. Large numbers of +flint implements have been collected from the Thames valley +and over the whole area of the rivers which have gravel +terraces along their course. Over a large sheet of gravel +at Southampton, whenever a large gravel pit is dug, implements +are found at the base of the gravel.<a name="FNanchor_A_17" id="FNanchor_A_17"></a><a href="#Footnote_A_17" class="fnanchor">[17]</a> The +occurrence of the mammoth and other arctic creatures in +the gravels shows that in the Glacial Period man was +contemporary with these animals. Remains in caves +tell the same story. In limestone caverns in Devon, +Derbyshire, and Yorkshire, implements made by man are +found in company with remains of the cave bear, cave +hyæna, lion, hippopotamus, rhinoceros, and other animals +either extinct or no longer inhabitants of this country—remains +which have been preserved under floors of stalagmite +deposited in the caves. In caves of central France +men have left carvings on bone and ivory, representing the +wild animals of that day—carvings which show a remarkable +artistic sense, and a keen observation of animal life. +Among them is a drawing of the mammoth on a piece of +mammoth ivory, showing admirably the appearance of +the animal, with his long hair, as he has been found +preserved in ice to the present day near the mouths of +Siberian rivers. Drawings of the reindeer, true to life, +are frequent.</p> + +<p><span class='pagenum'><a name="Page_99" id="Page_99">[Pg 99]</a></span> +Till recently very few Palæolithic implements had been +recorded as found in the Isle of Wight. In the Memoir +of the Geological Survey (1889) only one such is recorded, +found in a patch of brick earth near Howgate Farm, +Bembridge.<a name="FNanchor_A_18" id="FNanchor_A_18"></a><a href="#Footnote_A_18" class="fnanchor">[18]</a> A few more implements, which almost +certainly came from this brick-earth, have been found on +the shore since. In recent years a large number of Palæolithic +implements have been found at Priory Bay near +St. Helen's. They were first observed on the beach by +Prof. E. B. Poulton, F.R.S., in 1886, and were traced to +their source in the gravel in the cliff by Miss Moseley in +1902. From that time, and especially from 1904 onwards, +many have been found by Prof. Poulton, by R. W. Poulton +(and others). Up to 1909 about 150 implements had been +found, and there have been more finds since.<a name="FNanchor_B_19" id="FNanchor_B_19"></a><a href="#Footnote_B_19" class="fnanchor">[19]</a></p> + +<p><span class='pagenum'><a name="Page_100" id="Page_100">[Pg 100]</a></span> +The most important finds, besides those at Priory Bay, +have been those of Mr. S. Hazzledine Warren at Freshwater, +especially in trial borings in loam and clay below +the surface soil in a depression of the High Downs, south +of Headon Hill, at a level of about 360 ft. O.D., in which +a number of Palæolithic tools, flakes, and cores were +found<a name="FNanchor_A_20" id="FNanchor_A_20"></a><a href="#Footnote_A_20" class="fnanchor">[20]</a>. Isolated implements have been found in +recent years in various localities in the Island. There are +references to finds of implements at different times in the +past, but the descriptions are generally too vague to +conclude certainly to what date they belong. Much of +the gravel used in the Island comes from the angular +gravel on St. Boniface Down, or the high Plateau Gravel of +St. George's Down; but in the lower gravels and associated +brick earth, it is highly probable that more remains of +Palæolithic man will yet be found in the Island, and +quite possible that such have been found in the past, but +for want of accurate descriptions of the circumstances of +the finds are lost to us.</p> + +<p>We must pass on to the men of the Neolithic or later +stone age. The Palæolithic age was of very great duration, +much longer than all succeeding human history. Between +Palæolithic and Neolithic times there is in England a large +gap. In France various stages have been traced showing +a continual advance in culture. In England little, if anything, +has been found belonging to the intermediate stages. +Such remains may yet be found in caves, or in lower river +gravels, now buried below the alluvium. The gap between +Palæolithic and Neolithic is marked by the great amount +of river erosion which took place in the interval. +Palæolithic implements are found in gravels formed when +the rivers flowed some 100 feet above their present courses. +Take, <i>e.g.</i>, the Itchen at Southampton. After the 100 foot +gravels were deposited the river cut down, not merely to +its present level, but to an old bed now covered up by +<span class='pagenum'><a name="Page_101" id="Page_101">[Pg 101]</a></span> +various deposits beneath the river. After cutting down to +that bed the river laid down gravels upon it; and then—the +land standing at a higher level than to-day—the river +valley and the <a name="surrounding1"></a><a href="#typos">surrounding</a> country were covered by a +forest, which, as the climate altered and became damper, +was succeeded by the formation of peat. The land has +since sunk, and the peat, in parts 17 ft. thick, is now found +under Southampton Water, covered by estuarine silt. +The Empress Dock at Southampton was dug where a mud +bank was exposed at low water. The mud bank was +formed of river silt 12 to 17 feet thick. Below this was the +peat, resting on gravel. On the gravel horns of reindeer +were found. In the peat were large horn cores of the great +extinct ox, <i>Bos primigenius</i>, also horns of red deer, and +also in the peat were found neolithic flint chips, a circular +stone hammer head, with a hole bored through for a +wooden handle, and a large needle made of horn. Here, +at a great interval of time after Palæolithic man, as we see +by the history of the river we have just traced, we come +to the new race of men, the Neolithic.</p> + +<p>When Neolithic man appeared the land stood higher than +at present, though not so high as during great part of the +Pleistocene. Britain was divided from the Continent, +but the shores were a good way out into what is now sea +round the coasts, and forests clothed these further shores. +Remains of these, known as submerged forest, are found +below the tide mark round many parts of our coast. Peat +as at Southampton Docks, is found under the estuarine +mud off Netley. The wells at the Spithead Forts show an +old land surface with peat more than 50 feet below the +tide level. The old bed of the Solent river lies much lower +still—124 feet below high tide at Noman's Land Fort; +this channel was probably an estuary after the subsidence +of the land till it silted up with marine deposits to the +level on which the submerged forest grew.</p> + +<p>When the Solent and Southampton Water were wooded +<span class='pagenum'><a name="Page_102" id="Page_102">[Pg 102]</a></span> +valleys with rivers flowing down the middle, the Isle of +Wight rivers were tributaries to the Solent river, and the +forest, as might be expected, extended up their valleys, +and covered the low ground of the Island. Under the +alluvial flats are remains of buried forests. In digging a +well at Sandford in 1906 large trunks of hard oak were +found blocking the sinking of the well. When the land +sank the sea flowed up the river valleys, converting them +into strait and estuary, and largely filling up the channels +with the silt, which now covers the peat. In the silt of +Newtown river are found bones of <i>Bos primigenius</i>, +which was found with the Neolithic remains <a name="in"></a><a href="#typos">in</a> the peat +of Southampton docks.</p> + +<p>The remains of Neolithic man are not only found in +submerged forests, but over the present surface of the +land, or buried in recent deposits. He has left us the +tombs of his chiefs, known as long barrows—great mounds +of earth covering a row of chambers made of flat +stones, such as the mounds of New Grange in Ireland, and +the cromlechs or dolmens still standing in Wales and +Cornwall. These consist of a large flat or curved stone—it +may be 14 feet in length,—supported on three or four +others. Originally a great mound of earth or stones was +piled on top. These have generally been removed since +by the hand of later man. The stones have been taken +for road metal, the earth to lay on the land. The great +cromlech at Lanyon in Cornwall was uncovered by a +farmer, who had removed 100 cart loads of earth to lay +on his stony land before he had any idea that it was not +a natural mound. Then he came on the great cromlech +underneath. Another form of monument was the great +standing stone or menhir, one of which, the Longstone on +the Down above Mottistone still stands to mark the tomb +of some chieftain of, it may be, 4,000 years ago.</p> + +<p>The implements of Neolithic man are found all over +England, the smooth polished axe head, commonly called +<span class='pagenum'><a name="Page_103" id="Page_103">[Pg 103]</a></span> +a celt (Lat. <i>celtis</i>, a chisel), the chipped arrow head, the +flaked flint worked by secondary chipping on the edge +into a knife, or a scraper for skins; and much more common +than the implement, even of the simplest description, are +the waste flakes struck off in the making. Very few stone +celts have been found in the Isle of Wight. The flakes are +extremely numerous, and a scraper or knife may often be +found. They are turned up by the plough on the surface +of the fields, in the earth of which they have been preserved +from rubbing and weathering. They have however, acquired +a remarkable polish, or "patina"—how is not clearly +explained—which distinguishes their surface from the +waxy appearance of newly-broken flint. In places the +ground is so covered with flakes that we can have no doubt +that these are the sites of settlements. The implements +were made from the black flints fresh out of the chalk, +and we can locate the Neolithic flint workings. In our +northern range of downs where the strata are vertical the +layers of flint in the Upper Chalk run out on the top of +the downs, only covered with a thin surface soil. In places +where this soil has been removed—as in digging a quarry—the +chalk is seen to be covered with flakes similar to those +found on the lower ground, save that they are weathered +white from lying exposed on the hard chalk, instead of on +soft soil into which they would gradually sink by the +burrowing of worms. It is probable that these flakes +would be found more or less along the range of downs +under the surface soil.</p> + +<p>In places on the Undercliff have been found what are +known as Kitchen Middens—heaps of shells which have +accumulated near the huts of tribes of coast dwellers, who +lived on shellfish. One such was formerly exposed in the +stream below the old church at Bonchurch, and is believed +to extend below the foundations of the Church.</p> + +<p>After a long duration of neolithic times a great step in +civilisation took place with the introduction of bronze. +<span class='pagenum'><a name="Page_104" id="Page_104">[Pg 104]</a></span> +Bronze implements were introduced into this country +probably some time about B.C. 1800-1500; and bronze +continued to be the best material of manufacture till the +introduction of iron some two or three centuries before the +visit of Julius Caesar to these Islands. To the early bronze +age belong the graves of ancient chieftains known as +round barrows, of which many are to be seen on the Island +downs. Funeral urns and other remains have been found +in these, some of which are now in the museum at Carisbrooke +Castle. Belonging to later times are the remains +of the Roman villa at Brading and smaller remains of +villas in other places; and cemeteries of Anglo-Saxon +date, rich in weapons and ornaments, which have been +excavated on Chessil and Bowcombe Downs. But the +study of the remains of ancient man forms a science in +itself—Archæology. In studying the periods of Palæolithic +and Neolithic man we have stood on the borderland +where Geology and Archæology meet. We have seen that +vast geological changes have taken place since man appeared +on earth. We must remember that the geological +record is still in process of being written. It is not the +record of a time sundered from the present day, but continuous +with our own times; and it is by the study of +processes still in operation that we are able to read the +story of the past.</p> + +<div class="footnote"><p><a name="Footnote_A_17" id="Footnote_A_17"></a><a href="#FNanchor_A_17"><span class="label">[17]</span></a> Mr. W. Dale, F.S.A.</p></div> + +<div class="footnote"><p><a name="Footnote_A_18" id="Footnote_A_18"></a><a href="#FNanchor_A_18"><span class="label">[18]</span></a> See <a href="#Fig_9">figure 9</a>, p. 79.</p></div> + +<div class="footnote"><p><a name="Footnote_B_19" id="Footnote_B_19"></a><a href="#FNanchor_B_19"><span class="label">[19]</span></a> See account by R. W. Poulton in F. Morey's "Guide to the +Natural History of the Isle of Wight."</p></div> + +<div class="footnote"><p><a name="Footnote_A_20" id="Footnote_A_20"></a><a href="#FNanchor_A_20"><span class="label">[20]</span></a> Surv. Mem., I.W., 1921, p. 174.</p></div> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_105" id="Page_105">[Pg 105]</a></span></p> + +<div class="chapt_hdr">Chapter XIII.</div> +<div class="chapt_ttl">THE SCENERY OF THE ISLAND—<span class="smcap">Conclusion</span>.</div> + +<p>After studying the various geological formations that enter +into the composition of the Isle of Wight, and learning +how the Island was made, it will be interesting to take +a general view of the scenery, and see how its varied +character is due to the nature of its geology. It would +hardly be possible to find anywhere an area so small as +this little Island with such a variety of geological formations. +The result is a remarkable variety in the scenery.</p> + +<p>The main feature of the Island is the range of chalk +downs running east and west, and terminating in the bold +cliffs of white chalk at Freshwater and the Culvers. Here +we have vertical cliffs of great height, their white softened +to grey by weathering and the soft haze through which +they are often seen. In striking contrast of colour are the +Red Cliff of Lower Greensand adjoining the Culvers, and +the many-coloured sands of Alum Bay joining on to the +chalk of Freshwater. The summits of the chalk downs +have a characteristic softly rounded form, and the chalk +is covered with close short herbage suited to the sheep +which frequently dot the green surface. Where sheets of +flint gravel cap the downs, as on St. Boniface, they are +covered by furze and heather, producing a charming +variation from the smooth turf where the surface is chalk. +The Lower Greensand forms most of the undulating +country between the two ranges of downs; while the +Upper Greensand, though occupying a smaller area, produces +one of the most conspicuous features of the scenery—the +walls of escarpment that form the inland cliffs between +<span class='pagenum'><a name="Page_106" id="Page_106">[Pg 106]</a></span> +Shanklin and Wroxall, Gat Cliff above Appuldurcombe, the +fine wall of Gore Cliff above Rocken End, and the line of +cliffs above the Undercliff. To the Gault Clay is due the +formation of the Undercliff—the terrace of tumbled strata +running for miles well above the sea, but sheltered by an +upper cliff on the north, and in parts overgrown with +picturesque woods. The impervious Gault clay throws +out springs around the downs, which form the headwaters +of the various Island streams. The upper division of the +Lower Greensand, the Sandrock, forms picturesque undulating +foothills, often wooded, as at Apsecastle, and at +Appuldurcombe and Godshill Park. On a spur of the +Sandrock stands Godshill Church, a landmark visible +for miles around. At Atherfield we have a fine line of +cliffs of Lower Greensand, while the Wealden Strata on to +Brook form lower and softer cliffs.</p> + +<p>To the north of the central downs the Tertiary sands +and clays, often covered by Plateau gravel, form an +extended slope towards the Solent shore, much of it well +wooded, and presenting a charming landscape seen from +the tops of the downs. This slope of Tertiary strata is +deeply cut into by streams, which form ravines and +picturesque creeks, as Wootton Creek, 200 feet below the +level of the <a name="surrounding2"></a><a href="#typos">surrounding</a> country. While much of the +Island coast is a line of vertical cliff, the northern shores +are of gentler aspect, wooded slopes reaching to the +water's edge, or meadow land sloping gradually to the +sea level. Opposite the mouths of streams are banks of +shingle and sand dunes, forming the spits locally known as +"dovers." Some of these, in particular, St. Helen's Spit, +afford interesting hunting grounds for the botanist.</p> + +<p>The great variety of soil and situation renders the Isle +of Wight a place of interest to the botanist. We have +the plants of chalk downs, of the sea cliff and shore, of the +woods and meadows, of lane and hedgerow, and of the +marshes. The old villages of the Island, often occupying +<span class='pagenum'><a name="Page_107" id="Page_107">[Pg 107]</a></span> +very picturesque situations—as Godshill on a spur of the +southern downs, Newchurch on a bluff overlooking the +Yar valley, Shorwell nestling among trees in a south-looking +hollow of the downs, Brighstone with its old church +cottages and farmhouses among trees and meadows +between down and sea—the old and interesting churches, +the thatched cottages, the old manor houses of Elizabethan +or Jacobean date, now mostly farm houses, for which the +Island is famous, add to the varied natural beauty.</p> + +<p>One of the most characteristic features of the southern +coasts of the Island, should be mentioned, the Chines,—narrow +ravines which cut inland from the coast through +the sandstone and clays of the Greensand and Wealden +strata, and along the beds of which small streams flow to +the sea. Narrow and steep-sided,—the name by which +they are called is akin to <i>chink</i>—they are in striking +contrast to the more open valleys of the streams which +flow into the Solent on the north shore of the Island. The +most beautiful is Shanklin Chine. The cliff at the mouth +of the chine, just inside which stands a picturesque fisherman's +cottage with thatched roof, is 100 ft. high; and the +chasm runs inland for 350 yds., to where a very reduced +cascade (for the water thrown out of the Upper Greensand +by the Gault clay is tapped at its source for the town +supply) falls vertically over a ledge produced by hard +ferruginous beds of the Greensand. Above the cascade +the ravine runs on, but much shallower, for some 900 yards. +The lower ravine has much beauty, tall trees rising up the +sides, and overshadowing the chasm, the banks thickly +clothed with large ferns and other verdure. Much wilder +are the chines on the south-west of the Island. The +cascade at Blackgang falls over hard ferruginous beds (to +which the beds over which Shanklin cascade falls—though +on a smaller scale—probably correspond). The chine +above these beds, being hollowed out in the soft clays and +sands of the Sandrock series, is much more open. Whale +<span class='pagenum'><a name="Page_108" id="Page_108">[Pg 108]</a></span> +Chine is a long winding ravine between steep walls, the +stream at the bottom making its way through blocks of +fallen strata.</p> + +<p>The cause of these chines seems to be the same in all +cases. It may be noticed that Shanklin and Luccombe +chines are cut in the floors of open combes,—wide valleys +with gently sloping floors; and at each side of these chines +is to be seen the gravel spread over the floor of the old +valley. It can scarcely be doubted that these combes are +the heads of the valleys of the old streams, which flowed +down a gradual slope till they joined the old branch (or, +rather the old main river)<a name="FNanchor_A_21" id="FNanchor_A_21"></a><a href="#Footnote_A_21" class="fnanchor">[21]</a> of the Yar, flowing over land +extending far over what is now Sandown Bay. When the +sea encroached, and cut into the course of this old river, +and on till it made a section of what had been the left +slope of the valley, the old tributaries of the Yar now fell +over a line of cliff into the sea. They thus gained new +erosive power, and cut back at a much greater rate new +and deeper channels; with the result that narrow trenches +were cut in the floors of the old gently sloping valleys. +The chines on the S.W. coast are to be explained in a +similar way. They have been cut back with vertical sides, +because the encroachment of the sea caused the streams +to flow over cliffs, and so gave then power to cut back +ravines at so fast a rate that the weathering down of the +sides could not keep pace with it. The remarkable wind-erosion +of these bare south-westerly cliffs by a sort of +sand-blast driven before the gales to which that stretch +of coast is exposed has already been referred to.</p> + +<p>A few words in conclusion to the reader. I have tried +to show you something of the interest and wonder of the +story written in the rocks. We have seen something of the +world's making, and of the many and varied forms of life +which have succeeded each other on its surface. We have +had a glimpse of great and deep problems suggested, which +<span class='pagenum'><a name="Page_109" id="Page_109">[Pg 109]</a></span> +are gradually receiving an answer. Geology has the +advantage that it can be studied by all who take walks +in the country, and especially by those who visit any part +of the sea coast, without the need of elaborate and costly +scientific instruments and apparatus. Any country walk +will suggest problems for solution. I have tried to lead +you to observe nature accurately, to think for yourselves, +to draw your own conclusions. I have shown you how to +try to solve the questions of geology by looking around you +at what is taking place to-day, and by applying this +knowledge to explain the records which have reached us +of what has happened in the past. You are not asked to +accept the facts of the geological story on the word of the +writer, or on the authority of others, but to think for +yourselves, to learn to weigh evidence, to seek only to find +out the truth, whether it be geology you are studying or +any other subject, and to follow the truth whithersoever +it leads. + +<div class="footnote"><p><a name="Footnote_A_21" id="Footnote_A_21"></a><a href="#FNanchor_A_21"><span class="label">[21]</span></a> See <a href="#Page_91">p. 91</a>.</p></div> + +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_110" id="Page_110">[Pg 110]</a></span></p> + + <div class="caption1">TABLE OF STRATA</div> +<table bgcolor='#ffffff' summary="Strata Listing"> + <tr><td>Recent.</td><td colspan=4>Peat and River Alluvium.</td></tr> + <tr><td>Pleistocene.</td><td colspan=5>Plateau Gravels: Valley Gravels and Brick-Earth.</td></tr> + <tr><td rowspan=4>Tertiary</td><td rowspan=6><img src="images/brace_lf1.png" width="20" height="460" alt="left brace"></td><td>Pliocene<br>Miocene</td><td><img src="images/brace_rt3.png" width="18" height="29" alt="right brace"></td><td>Absent from the Isle of Wight.</td></tr> + <tr><td>Oligocene</td><td><img src="images/brace_lf2.png" width="19" height="235" alt="left brace"></td><td> + <table summary="sublist"> + <tr><td> + <table summary="sublist"> + <tr><td>Hamstead</td><td><img src="images/brace_lf3.png" width="18" height="69" alt="left brace"></td><td>Marine, Corbula Beds<br>Freshwater & Estuarine.</td></tr> + </table> + </td></tr> + <tr><td> + <table summary="sublist"> + <tr><td>Bembridge<br> Beds</td><td><img src="images/brace_lf3.png" width="18" height="69" alt="left brace"></td><td>Bembridge Marls<br>Bembridge Limestone</td></tr> + </table> + </td></tr> + <tr><td>Osborne and St. Helen's Beds.</td></tr> + <tr><td> + <table summary="sublist"> + <tr><td>Headon<br> Beds</td><td><img src="images/brace_lf3.png" width="18" height="69" alt="left brace"></td><td>Upper. Freshwater and Brackish<br>Middle. Marine<br>Lower. Freshwater and Brackish</td></tr> + </table> + </td></tr> + </table></td> + </tr> + <tr> + <td rowspan=2>Eocene</td><td rowspan=2><img src="images/brace_lf3.png" width="18" height="129" alt="left brace"></td><td> + <table summary="sublist"> + <tr><td>Barton<br>Beds</td><td><img src="images/brace_rt3.png" width="18" height="29" alt="right brace"></td><td>Barton Sand.<br>Barton Clay.</td></tr> + </table></td> + </tr> + <tr><td>Bracklesham Beds.<br>Bagshot Sands<br>London Clay<br>Plastic Clay (Reading Beds)</td></tr> +</table> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_111" id="Page_111">[Pg 111]</a></span></p> + +<table bgcolor='#ffffff' summary="Strata List"> + <tr><td rowspan=2>Mesozoic or<br>Secondary</td><td rowspan=2><img src="images/brace_lf1.png" width="20" height="560" alt="left brace"></td><td>Upper<br>Cretaceous<br><img src="images/cleardot.png" width="0" height="260" alt=" "></td><td><img src="images/brace_lf2.png" width="19" height="285" alt="left brace"><br><img src="images/cleardot.png" width="0" height="280" alt=" "></td> + <td> + <table summary="sublist"> + <tr><td><table summary="sublist"><tr><td>White<br>Chalk</td><td><img src="images/brace_lf3.png" width="18" height="59" alt="left brace"></td><td>Upper Chalk (Chalk with flints)<br>Middle Chalk (Chalk without flints)</td></tr></table></td></tr> + <tr><td><table summary="sublist"><tr><td>Lower<br>Chalk</td><td><img src="images/brace_lf3.png" width="18" height="99" alt="left brace"></td><td>A. plenus Marls<br>Grey Chalk<br>Chalk Marl<br>Chloritic Marl</td></tr></table></td></tr> + <tr><td><table summary="sublist"><tr><td>Selbornian</td><td><img src="images/brace_lf3.png" width="18" height="89" alt="left brace"></td><td> + <table summary="sublist"> + <tr><td>Upper<br>Greensand</td><td><img src="images/brace_lf3.png" width="18" height="69" alt="left brace"></td><td>Chert Beds<br>Sandstone and<br> Rag Beds</td></tr> + <tr><td>Gault</td><td> </td><td> </td></tr> + </table></td> + </tr> + </table> + </td></tr> + <tr><td> + <table summary="sublist"> + <tr><td> + Lower<br>Cretaceous</td><td><img src="images/brace_lf2.png" width="19" height="235" alt="left brace"></td><td> + <table summary="sublist"> + <tr><td>Lower<br> Greensand</td><td><img src="images/brace_lf3.png" width="18" height="109" alt="left brace"></td><td>Carstone<br>Sandrock and Clays<br>Ferruginious Sands<br>Atherfield Clay<br>Perna Bed</td></tr> + <tr><td>Wealden</td><td><img src="images/brace_lf3.png" width="18" height="69" alt="left brace"></td><td>Shales<br>Variegated Marls</td></tr> + </table></td></tr> + </table></td></tr> + </table> + </td> + </tr> +</table> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Page_112" id="Page_112">[Pg 112]</a></span></p><br /> + +<div class="caption2">FOR FURTHER STUDY.</div> + +<p>Memoirs of the Geological Survey. General Memoir of +the Isle of Wight, date 1889. New edition, entitled "A +short account of the Geology of the Isle of Wight," by H. J. +Osborne White, F.G.S., 1921, price 10s. The Memoirs are +the great authority for the Geology of the Island: technical; +books for Geologists. The New Edition is more condensed +than the original, but contains much later research. +Mantell's "Geological Excursions round the Isle of +Wight," 1847. By one of the great early geologists. +Long out of print, but worth getting, if it can be picked +up second-hand.</p> + +<p>Norman's "Guide to the Geology of the Isle of Wight," +1887, still to be obtained of Booksellers in the Island. +Gives details of strata, and lists of fossils, with pencil +drawings of fossils.</p> + +<p>Other books bearing on the subject have been mentioned +in the text and foot-notes.</p> + +<p>An excellent geological map of the Island, printed in +colour, scale 1 in. to the mile, full of geological information, +is published by the Survey at 3s.</p> + +<p>A good collection of fossils and specimens of rocks from +the various strata of the Isle of Wight has recently been +arranged at the Sandown Free Library, and should be +visited by all interested in the Geology of the Island. +It should prove a most valuable aid to all who take up the +study, and a great assistance in identifying any specimens +they may themselves find.</p> +<p> </p> +<p> </p> + +<p><span class='pagenum'><a name="Geol_Map" id="Geol_Map">[Geol Map]</a></span></p> + +<div class="center"> + <a href="images/grologic_map.png"><img src="images/grologic_map_sm.png" width="600" height="410" border="0" alt="" title="" /></a><br> + <span class="smaller">Click on map for larger view.</span><br /><br /> + Geological Map of the Isle of Wight<br /><br /> +</div> +<p> </p> +<p> </p> + +<span class='pagenum'><a name="Page_113" id="Page_113">[Pg 113]</a></span><br /> +<div class="caption3">INDEX</div> +<br /> +<br /> +Words in Italics refer to a page where the meaning of a<br /> +term is given.<br /> +<br /> +<br /> +Agates, <a href="#Page_22">22</a>, <a href="#Page_41">41</a>, <a href="#Page_50">50</a><br /> +<br /> +Alum Bay, <a href="#Page_56">56-62</a><br /> +<br /> +Ammonites, <a href="#Page_32">32</a>, <a href="#Page_34">34</a>, <a href="#Page_39">39</a>, <a href="#Page_44">44</a><br /> +<br /> +<i>Anticline</i>, <a href="#Page_12">12</a><br /> +<br /> +Astronomical Theory of Ice Age, <a href="#Page_83">83</a>, <a href="#Page_85">85</a><br /> +<br /> +Atherfeld, <a href="#Page_29">29</a><br /> +<br /> +Avon River, <a href="#Page_94">94</a><br /> +<br /> +<br /> +Barrows, <a href="#Page_102">102</a>, <a href="#Page_104">104</a><br /> +<br /> +Barton, <a href="#Page_61">61</a><br /> +<br /> +Belemnites, <a href="#Page_33">33</a><br /> +<br /> +Bembridge Limestone, <a href="#Page_65">65</a><br /> + — shingle at, <a href="#Page_95">95</a><br /> +<br /> +Benettites, <a href="#Page_27">27</a><br /> +<br /> +"Blue Slipper," <a href="#Page_15">15</a><br /> +<br /> +Bonchurch, <a href="#Page_50">50</a>, <a href="#Page_103">103</a><br /> +<br /> +Bos primigenius, <a href="#Page_101">101</a>, <a href="#Page_102">102</a><br /> +<br /> +Botany, <a href="#Page_106">106</a><br /> +<br /> +Bracklesham, <a href="#Page_59">59</a>, <a href="#Page_60">60</a><br /> +<br /> +Brading Harbour, <a href="#Page_90">90</a>, <a href="#Page_91">91</a><br /> +<br /> +Bronze age, <a href="#Page_103">103</a><br /> +<br /> +Brook, <a href="#Page_29">29</a><br /> +<br /> +Building Stone, <a href="#Page_39">39</a>, <a href="#Page_65">65</a><br /> +<br /> +<br /> +Carstone, <a href="#Page_26">26</a>, <a href="#Page_35">35</a><br /> +<br /> +Chalcedony, <a href="#Page_22">22</a>, <a href="#Page_41">41</a>, <a href="#Page_50">50</a><br /> +<br /> +Chale, <a href="#Page_33">33</a><br /> +<br /> +Chalk, divisions of, <a href="#Page_45">45</a>, <a href="#Page_51">51</a>, <a href="#Page_52">52</a><br /> + — Marl, <a href="#Page_45">45</a><br /> + — Rock, <a href="#Page_45">45</a><br /> +<br /> +Chalybeate Springs, <a href="#Page_25">25</a><br /> +<br /> +Chert, <a href="#Page_39">39</a><br /> +<br /> +Chloritic Marl, <a href="#Page_44">44</a><br /> +<br /> +Climate.<br /> +<br /> +Coal, <a href="#Page_8">8</a>, <a href="#Page_61">61</a><br /> +<br /> +Colwell Bay, <a href="#Page_64">64</a><br /> +<br /> +Compton Bay, <a href="#Page_31">31</a>, <a href="#Page_39">39</a><br /> +<br /> +Conglomerate, modern, <a href="#Page_25">25</a><br /> +<br /> +"Crackers," <a href="#Page_32">32</a><br /> +<br /> +Cretaceous.<br /> +<br /> +Crioceras, <a href="#Page_34">34</a><br /> +<br /> +Current Bedding, <a href="#Page_27">27</a><br /> +<br /> +Cycads.<br /> +<br /> +<br /> +Denudation, <a href="#Page_3">3</a>, <a href="#Page_12">12</a>, <a href="#Page_76">76</a>, <a href="#Page_80">80</a>, <a href="#Page_82">82</a><br /> +<br /> +<i>Dip</i>, <a href="#Page_11">11</a><br /> +<br /> +<br /> +Echinoderms, <a href="#Page_48">48</a>, <a href="#Page_52">52</a><br /> +<br /> +Eocene, <a href="#Page_54">54</a><br /> +<br /> +Erosion, marine, <a href="#Page_4">4</a><br /> + " pre-Tertiary, <a href="#Page_54">54</a><br /> +<br /> +<i>Escarpment</i>, <a href="#Page_14">14</a><br /> + +<p><span class='pagenum'><a name="Page_114" id="Page_114">[Pg 114]</a></span> +<i>Faults</i>, <a href="#Page_13">13</a><br /> +<br /> +Fault at Brook, <a href="#Page_30">30</a><br /> +<br /> +Flint, origin of, <a href="#Page_47">47</a><br /> + " implements, <a href="#Page_97">97</a><br /> +<br /> +Flora, Alum Bay, <a href="#Page_59">59</a><br /> + " Eocene, <a href="#Page_58">58</a>, <a href="#Page_62">62</a><br /> + " Wealden, <a href="#Page_18">18</a>, <a href="#Page_27">27</a><br /> +<br /> +Foraminifera, <a href="#Page_42">42</a>, <a href="#Page_61">61</a><br /> +<br /> +<br /> +Gat Cliff, <a href="#Page_38">38</a><br /> +<br /> +Gault, <a href="#Page_37">37</a><br /> +<br /> +Glacial Period, <a href="#Page_77">77-85</a><br /> +<br /> +Glauconite, <a href="#Page_24">24</a>, <a href="#Page_39">39</a>, <a href="#Page_44">44</a><br /> +<br /> +Gore Cliff, <a href="#Page_39">39</a>, <a href="#Page_44">44</a><br /> +<br /> +Greensand, Lower, <a href="#Page_23">23-36</a><br /> + " Upper, <a href="#Page_37">37</a><br /> +<br /> +Gravels, <a href="#Page_50">50</a>, <a href="#Page_79">79</a>, <a href="#Page_89">89</a>, <a href="#Page_93">93-95</a><br /> +<br /> +<br /> +Hamstead, <a href="#Page_65">65</a>, <a href="#Page_67">67</a><br /> +<br /> +Headon Hill, <a href="#Page_62">62-64</a><br /> +<br /> +Hempstead, see Hamstead.<br /> +<br /> +Hyopotamus, <a href="#Page_69">69</a><br /> +<br /> +<br /> +Ice Age, <a href="#Page_77">77-85</a><br /> +<br /> +Iguanodon, <a href="#Page_20">20</a><br /> +<br /> +Insect Limestone, <a href="#Page_67">67</a><br /> +<br /> +Iron Ore, <a href="#Page_22">22</a>, <a href="#Page_24">24</a><br /> +<br /> +Iron pyrites, <a href="#Page_22">22</a><br /> +<br /> +<br /> +Landslips, <a href="#Page_25">25</a>, <a href="#Page_38">38</a><br /> +<br /> +Limnæa, <a href="#Page_63">63</a>, <a href="#Page_64">64</a>, <a href="#Page_66">66</a><br /> +<br /> +Lobsters, Atherfield, <a href="#Page_32">32</a><br /> +<br /> +London Clay, <a href="#Page_57">57</a><br /> +<br /> +Luccombe, Landslip at, <a href="#Page_25">25</a><br /> +<br /> +<br /> +Mammalian Remains, <a href="#Page_66">66</a>, <a href="#Page_69">69</a><br /> +<br /> +Mammoth, <a href="#Page_77">77</a>, <a href="#Page_81">81</a><br /> +<br /> +Marvel, <a href="#Page_35">35</a><br /> +<br /> +Medina, <a href="#Page_93">93</a><br /> +<br /> +Melbourn Rock, <a href="#Page_45">45</a><br /> +<br /> +Miocene, <a href="#Page_69">69</a>, <a href="#Page_71">71</a>, <a href="#Page_76">76</a><br /> +<br /> +<br /> +Nautilus, <a href="#Page_32">32</a>, <a href="#Page_45">45</a><br /> +<br /> +Needles, <a href="#Page_4">4</a><br /> +<br /> +Neolithic Man, <a href="#Page_100">100</a><br /> +<br /> +Newtown River, <a href="#Page_102">102</a><br /> +<br /> +Nummulites, <a href="#Page_61">61</a><br /> +<br /> +<br /> +Oligocene, <a href="#Page_63">63</a><br /> +<br /> +<br /> +Palæolithic Man, <a href="#Page_97">97</a><br /> +<br /> +Perna Bed, <a href="#Page_23">23</a>, <a href="#Page_31">31</a><br /> +<br /> +Pine Raft, <a href="#Page_29">29</a><br /> +<br /> +Planorbis, <a href="#Page_63">63</a>, <a href="#Page_64">64</a>, <a href="#Page_66">66</a><br /> +<br /> +Plastic Clay, <a href="#Page_57">57</a><br /> +<br /> +Priory Bay, <a href="#Page_99">99</a><br /> +<br /> +Purbeck Marble, <a href="#Page_16">16</a><br /> +<br /> +<br /> +Quarr, <a href="#Page_65">65</a><br /> +<br /> +<br /> +Rag, <a href="#Page_38">38</a><br /> +<br /> +Rock (place), <a href="#Page_35">35</a><br /> +<br /> +Roman Villas, <a href="#Page_104">104</a><br /> +<br /> +<br /> +St. Boniface Down, <a href="#Page_50">50</a>, <a href="#Page_100">100</a>, <a href="#Page_105">105</a><br /> +<br /> +St. George's Down, <a href="#Page_79">79</a>, <a href="#Page_100">100</a><br /> +<br /> +Sandown Anticline, <a href="#Page_11">11-13</a>, <a href="#Page_89">89</a><br /> +<br /> +Sandrock, <a href="#Page_25">25</a>, <a href="#Page_35">35</a><br /> +<br /> +Scaphites, <a href="#Page_34">34</a><br /> +<br /> +Scenery, <a href="#Page_105">105</a><br /> +</p> + +<p><span class='pagenum'><a name="Page_115" id="Page_115">[Pg 115]</a></span> +<br /> +Sea Urchins, <a href="#Page_48">48</a>, <a href="#Page_52">52</a>,<br /> +<br /> +Shanklin Chine, <a href="#Page_107">107</a><br /> +<br /> +Solent, <a href="#Page_94">94</a><br /> +<br /> +Southampton Dock, <a href="#Page_101">101</a><br /> + " Water, <a href="#Page_94">94</a><br /> +<br /> +Sponges in Flint, <a href="#Page_47">47</a><br /> +<br /> +Stone Age, <a href="#Page_97">97</a><br /> +<br /> +Strata, Table of, <a href="#Page_110">110</a>, <a href="#Page_111">111</a><br /> +<br /> +<i>Strike</i>, <a href="#Page_11">11</a><br /> +<br /> +Submerged Forest, <a href="#Page_101">101</a><br /> +<br /> +Swanage, <a href="#Page_93">93</a><br /> +<br /> +<i>Syncline</i>, <a href="#Page_12">12</a><br /> +<br /> +<br /> +Table of Strata, <a href="#Page_110">110</a>, <a href="#Page_111">111</a><br /> +<br /> +Tertiary, <a href="#Page_54">54</a><br /> +<br /> +Totland Bay, <a href="#Page_63">63</a>, <a href="#Page_95">95</a><br /> +<br /> +Tufa, <a href="#Page_45">45</a><br /> +<br /> +Turtle, <a href="#Page_58">58</a>, <a href="#Page_65">65</a>, <a href="#Page_68">68</a><br /> +<br /> +<br /> +Undercliff, formation of, <a href="#Page_25">25</a>, <a href="#Page_38">38</a><br /> +<br /> +<br /> +Volcanic Action, <a href="#Page_5">5</a><br /> +<br /> +<br /> +Wealden, <a href="#Page_15">15</a><br /> +<br /> +Whitcliff Bay, <a href="#Page_56">56-67</a><br /> +<br /> +Wood, Fossil, <a href="#Page_8">8</a>, <a href="#Page_15">15</a>, <a href="#Page_18">18</a>, <a href="#Page_27">27</a>, <a href="#Page_29">29</a><br /> +<br /> +<br /> +Yar, Eastern, <a href="#Page_89">89-91</a><br /> +<span style="margin-left: 1em;">Western, <a href="#Page_92">92</a></span><br /> +<br /> +<br /> +Zones of Chalk, <a href="#Page_51">51</a>, <a href="#Page_52">52</a><br /> +<p> </p> +<p> </p> + +<span class='pagenum'><a name="Page_116" id="Page_116">[Pg 116]</a></span> +<i>Printed by The Crypt House Press, Bell Lane, Gloucester.</i> +<p> </p> +<p> </p> + + + + + + + + + + + +<pre> + + + + + +End of the 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