NA TURE 



169 



THURSDAY, DECEMBER 23, 1897. 



THE GROWTH OF GEOLOGICAL IDEAS. 



The Founders of Geology. By Sir Archibald Geikie. 

 Pp. X + 297. (London: Macmillan and Co., Ltd., ►1897.) 



THE truths of science cannot be more impressively 

 taught than by a sketch of the process by which 

 the knowledge has been arrived at, and in no way can 

 that history be more forcibly conveyed than in the 

 biographies of those pioneers who first interpreted the 

 phenomena for us. We may have wondered why the 

 truth was not sooner grasped, but by this method of 

 treating the subject we see what imperfection of evidence 

 or prejudice stood in the way, and learn to appreciate 

 the true spirit of original research which eventually rises 

 above and overcomes all difficulties. 



Sir Archibald Geikie has given a sketch of the 

 founders of geology in his, now happily well-known, 

 lucid style. It is necessarily only a selection, and 

 accident or design has led him to make such a selection 

 of points in the development of the subject as has 

 enabled him to write what may be called an " apprecia- 

 tion " of the French school of geologists, and to dwell 

 very fully on the work of some of them whose claims to 

 recognition have hitherto been too much overlooked. 



In the earlier stages of research all those who studied 

 the composition of the earth's crust were called miner- 

 alogists, and any stony fragments which they dug out 

 of the earth were their fossils. When men began to 

 distinguish between bodies of organic and inorganic 

 origin, they spoke of the pieces of rock and other 

 mineral matter as native fossils, considering them as 

 part of the original mass, while they called the remains 

 of plants and animals extraneous fossils. It was only 

 in comparatively recent times that the word fossil was 

 applied exclusively to the remains of organisms. When 

 the older writers speculated upon the manner in which 

 the earth's crust had been brought into its present con- 

 dition, they entitled their results "theories of the earth," 

 which corresponded generally to our modern works on 

 the principles of geology. Though they too often 

 generahsed on insufficient data, or wrested their judg- 

 ment to support an early-formed opinion, they all pre- 

 tended that their theories were founded on the study 

 of nature ; but we find many a good observation and 

 sound inference buried under such a load of bad reason- 

 ing, and accompanied by such a cloud of foolish observa- 

 tions, that the writer's credit as a witness was destroyed, 

 and even what was good in him lost sight of 



Our author passes with very brief notice over all the 

 writers earlier than the eighteenth century, and devotes 

 the greater part of his first lecture to a sketch of the 

 work of Guettard : in a few clever touches he brings 

 before us the personality of that remarkable man. 

 Guettard first put into practice the proposal made by 

 Lister in 1683, and constructed a map on which he 

 showed the general surface distribution of the various 

 kinds of rock as they occurred in broad belts in and 

 around the Paris Basin, and even marked on it the 

 places where he had found fossils. Later on, when a 

 good topographical map of France had been produced, 



NO. 1469. VOL 57] 



he indicated on it the characters of the rock over a very 

 large area, completing the mineralogical survey of no 

 fewer than sixteen sheets of the map. This was a work 

 of great labour, and one involving very close observation, 

 especially as he does not seem to have had any clear 

 idea of the sequence of formations or of geological 

 structure to guide him. Guettard was the first to 

 recognise the ancient volcanoes of Auvergne, and 

 deserves great credit for his able memoir on the mean- 

 ing of the occurrence of the remains of shells and other 

 organisms in the rocks. But the battle had long been 

 raging between those who maintained that the fossils 

 were mere lusus 7taturce, and those who held that they 

 represented plants and animals which once lived under 

 conditions analogous to those of recent times, and were 

 buried, as are dead organisms, in the mud and sand of 

 to-day. In this long controversy many Italian and 

 English geologists did good service, notably Agostino 

 Scilla and Dr. John Woodward, who combated espe- 

 cially the erroneous views of Dr. Elie Camerarius ; 

 and although their work was hampered by the attempt 

 to accommodate all their explanations to the received 

 interpretation of the Scriptural account of the deluge, 

 still the search for facts to support their theories helped 

 on the work by calling attention to phenomena which 

 might otherwise have long passed unobserved. 



In his second lecture our author gives a sketch of the 

 life and work of Desmarest. He tells us of the diffi- 

 culties and struggles of his early life ; of his official 

 work in connection with the efforts made by the French 

 Government in the middle of the last century to develop 

 the industries of the country ; and of the influence which 

 the eloquent writings of BufTon had upon him. Des- 

 marest was struck by the correspondence between the 

 opposite clifl[s of France and England which had already 

 been pointed out by Guettard, and still earlier by 

 Verstegan. Supporting by biological evidence the idea 

 thus suggested, Desmarest arrived at the conclusion 

 that the channel which now separated them had been 

 cut by the currents of the sea. 



His official duties necessitated much travel, but in 

 the intervals of leisure he revisited and more closely 

 examined localities which suggested subjects for further 

 research. In this way he was led to study the origin of 

 basalt, which had been a fruitful theme of controversy 

 for many a long year. He noticed the prismatic struc- 

 ture of the basalts of Auvergne, and recognised them as 

 ancient lavas, and, from descriptions of the general 

 appearance of the columnar rocks of the Giant's Cause- 

 way, and an examination of hand specimens, he inferred 

 that they were the same. 



He explained the origin of valleys by referring them 

 to the action of the streams which flow in them. This 

 view had evidently been present to the mind of Avicenna, 

 who in the tenth century maintained that mountains were 

 made to stand out by the excavation of the valleys 

 between them, while our great naturalist Ray dwelt upon 

 the operation of streams in the degradation of the land, 

 pointing out that the land must necessarily be eventually 

 reduced below sea level by such agencies. 



We are told how from an examination of volcanic 

 phenomena, and in the attempt to correlate them, 

 Desmarest was led to generalise upon the relation of 



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