HARD WICKE' S S CIENCE - G O SSIP. 



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published. At that time, said Dr. Taylor, both the 

 Cambrian and Silurian rock formations — two of the 

 thickest in this country — were very imperfectly under- 

 stood. There was no Devonian formation as it now 

 stands, no Permian formation, and the Neocomian, 

 which comes between the chalk and part of the 

 Wealden, had not been recognised. There was a 

 great break between the close of the chalk period 

 and the commencement of the Tertiary period, which 

 has since been filled up in part by the discovery in 

 Denmark of deposits of intervening age, and still 

 more so by certain thick beds in the Western States 

 of America, Dacota for instance. In 1837 the great 

 Tertiary system was practically waste ground. Lyell 

 was investigating it, and his subsequent divisions of 

 it, based upon the relative percentages of recent shells 

 which the older and younger strata of this formation 

 contained, were accepted by geologists all over the 

 world, and have been retained ever since. At the 

 period of which he spoke, our Suffolk Red crag was 

 supposed to be the newest formation. The Boulder 

 clays, gravels and sands which mask the northern, 

 midland, and eastern parts of England, were called 

 Diluvian, and even Dean Buckland wrote a paper 

 to prove that these deposits had been left by the 

 Noachian deluge, although he was wise and candid 

 enough to write a recantatory tract afterwards, when 

 he had learned more, to disprove his own former 

 opinion. Subsequently it was found that a special 

 period would have to be provisionally formed to 

 include the same deposits. This is now known as 

 the Great Ice Age, and the marvellous way in which 

 the evidence came in to prove, that we had a glacial 

 epoch at the time when our Suffolk and Norfolk 

 boulder clays were deposited, was detailed at some 

 length by the speaker. Lyell's work on the ' ' Prin- 

 ciples of Geology " had but recently appeared in 

 1S37, and was beginning to make headway. Previous 

 to that, it had been imagined that geological forma- 

 tions were the result of catastrophic action, 'that is to 

 say, of sudden and violent changes, but Lyell demon- 

 strated that the physical changes now in force upon 

 the face of the earth, if given time, would effect all 

 the mighty results with which geology had to deal. 



At that time the theories held concerning earth- 

 quakes and volcanoes were very different from what 

 they are now. Even the great Humboldt died be- 

 lieving that volcanoes were simply so many blisters 

 on the earth's crust, and he went so far as to think 

 that they were suddenly and violently erupted. Mr. 

 Scrope, Daubigny, and others, were in favour of 

 volcanic mountains being gradually - accumulated 

 growths, and this is now known to be correct. The 

 ideas concerning the interior of the earth were then 

 exceedingly vague, and now seem exceedingly funny. 

 The earth's crust was regarded as much thinner than 

 we now know it to be. The whole of the interior 

 was believed to be molten, whereas we know that it 

 is as rigid as cast steel, so that the idea of a thin 



crust blistering in the shape of volcanoes and frac- 

 turing in the shape of faults was a very easy concep- 

 tion. Geologists at that time lifted up continents 

 and set them down without any difficulty on this easy 

 theory. They brought seas rushing over suddenly- 

 submerged land, with such violence, that it was no 

 wonder they easily interpreted the phenomenon of 

 the drift, with its strange beds of boulders and 

 variously-disposed materials. 



Granite was believed at that time to have been the 

 first cooled crust of the earth, whereas it is known 

 that granite in every instance has been formed under 

 exceedingly great rock pressure, never less than that 

 of thirty thousand feet of overlying rocks, and that 

 the reason why it appears at the surface is because 

 those materials had been stripped away by denuda- 

 tion. Between thirty and forty years ago, a few 

 gentlemen commenced a new line of investigation 

 into rocky structures. Dr. Sorby, of Sheffield, cut, 

 sliced, and polished thin sections of granite, and 

 examined them under the microscope. His paper on 

 the results he arrived at, read before the Geological 

 Society in 1862, effected a revolution in geological 

 investigation. From that moment the microscope 

 has been a geological instrument, and the discoveries 

 made by it have been really marvellous. 



In 1861, Professor Dawson, of Montreal, announced 

 the existence of vast masses of rock older than the 

 Cambrian formation in the district watered by the 

 River St. Lawrence. These were called Laurentian. 

 He affirmed that certain beds of altered limestone in 

 these rocks had been deposited by a minute organism, 

 which he named Eozoon. This Laurentian series of 

 rocks has since then been found in almost every part 

 of the earth's dry-land crust. It is the core, so to 

 speak, the central part of the known stratified rocks 

 of the earth, although the name of Archean is now 

 generally given to this formation. 



Dr. Taylor then took up the second part of his 

 subject, which dealt with the fossil remains in the 

 rocks. The idea, fifty years ago, was that each geo- 

 logical formation represented a special creation and a 

 special extinction. Creation was then believed to be 

 sudden, after the old idea, and extinction to be 

 equally brief. This idea maintained its ground up to 

 a quarter of a century ago in some geological manuals. 

 Darwin's works first started the idea of a continuous 

 stream of life upon the globe, which idea hitherto 

 had been checked by the belief that, at the close of 

 the Primary epoch, there had been a great break in 

 the life of the world, and that a similar break occurred 

 at the close of the Secondary epoch. But the fact, 

 that in other parts of the world deposits had been 

 discovered containing fossils which bracketed together 

 and filled up these gulfs, not only met the difficulty, 

 but established for ever the fact, that there had been 

 a continuous stream of life upon our planet. The 

 fossil remains known in the earth's crust fifty years 

 ago were not a twentieth part of those known to-day. 



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