November 6, 1919] 



NATURE 



20- 



THE EXPANSION OF GEOLOGY. 



By Prof. T. G. Bonnev, F.R.S. 



I 



IN the fifty years since this journal began, the 

 progress in geology has kept pace with that 

 of the other natural sciences. In regard to them, 

 in an article contributed to the first volume, I 

 wrote of what had been done and what yet 

 required to be done for their study in Cambridge, 

 where I was then resident, and whither I have 

 since returned. The changes may almost be called 

 a transformation. The museums and laboratories, 

 though the supply is not yet quite equal to the 

 demand, far surpass what we desired in those 

 early days, and the class-list of the Natural 

 Sciences Tripos, instead of containing about a 

 dozen names, had risen before the war to fully 

 130. The same is true of the other older universi- 

 ties, while more than as many, non-existent fifty 

 years ago, are now busily engaged in educating 

 natural science students. 



But to refer to geology only. In 1869 even 

 the geography of considerable regions on the 

 earth's surface was unknown. There were large 

 areas in Africa, away from the coasts, where only 

 here and there had a traveller passed. Hundreds 

 of square miles about the North and South Poles 

 were blanks upon the maps. With the exception 

 of Western Europe, North America east of 

 the Rocky Mountains, some portions of Asia, 

 and a little of Australia, geological knowledge was 

 very limited. Now careful surveys have been 

 made far beyond the original boundaries, and it 

 is not too much to say that a general idea has 

 been obtained of the geology of the earth as a 

 whole, for, in addition to exploration of its 

 surface, deep-sea sounding has revealed the 

 nature of the deposits now forming on the ocean 

 floor. 



The advances in stratigraphical knowledge have 

 told on every branch of geology, but especially 

 on palaeontology. Much valuable work had no 

 doubt been done by 1869 on the Corals, the 

 Echinoderms, the Crustaceans, the Brachiopods, 

 the Molluscs, and the Vertebrates, but great dis- 

 coveries have been made, particularly in regard 

 to the last. The work on them, begun by Cuvier 

 and carried on by Owen, has now been extended 

 to most parts of the globe. Even so near as 

 Belgium, the buried ravines of Bernissart have 

 yielded up whole skeletons of the Iguanodon ; the 

 more central parts of North America show that, 

 when the Rocky Mountains had partly begun to 

 rise, reptiles, stranger in form and vaster in 

 bulk than the founders of palaeontology had 

 imagined, haunted their swamps, and lakes, and 

 rivers. Cope and Marsh, fifty years ago, were 

 only beginning their work. Such giant reptiles 

 as Brontosaurus ; Atlantosaurus ; Diplodocus, 

 with its inordinately long neck and tail ; ; 

 Stegosaurus, with its strangely serrate back ; i 

 and Triccratops, with its horned and armoured 

 head, have all been reconstructed. Some century 

 and a half ago a forerunner of the sea-serpent 

 NO. 2610, VOL. 104] 



had been discovered at Maestricht, but the list 

 of Mosasauroid reptiles has been much augmented 

 from the inhabitants of the inland seas of late 

 Cretaceous age near the Rocky Mountains of the 

 present day. Dentigerous birds, and the Archseo- 

 pteryx, half-bird, half-reptile, have been dis- 

 covered, and some of the earliest Tertiary mam- 

 mals, again more especially in Central North 

 America, are no less weird in shape than the 

 above-mentioned reptiles. 



Since the publication of the "Origin of 

 Species," which antedated that of Nature by ten 

 years, scientific palaeontology may almost be said 

 to have been born. Missing links in the chain 

 of living creatures have been found,, gaps in 

 knowledge have been filled in, difficulties which 

 raised opposition from not a few good naturalists 

 have been removed ; evolution has passed from 

 the stage of hypothesis to that of theory, and 

 extended from natural history to other branches 

 of science and into yet wider fields. The pedi- 

 gree of not a few forms of life has been con- 

 structed, so that "zoning" by fossils has greatly 

 aided the stratigrapher, and the zoologist finds 

 it possible in many cases to retrace the steps of 

 that pedigree until, in this tree of life, the twigs 

 are followed down into the branches, and the 

 branches to the primary stems, though, notwith- 

 standing recent discoveries in regard to the fauna 

 of early Cambrian times, not a few pages have 

 disappeared from the history of life, especially 

 in its opening chapter. Discovery is now pro- 

 ceedyig with quickened pace in the history of 

 plant life, so that when Nature celebrates its 

 centenary the zoology and botany of the world 

 will undoubtedly be understood far more com- 

 pletely than they are at the present day. 



In i86g petrology was at a low ebb. Maccul- 

 loch and De la Beche had done what was possible 

 without the microscope, but the great majority of 

 field-workers remained well contented if they 

 could recognise the commoner igneous rocks and 

 vaguely identify the metamorphic. Clifton Sorby, 

 by applying the microscope to petrological study, 

 had pointed out, nearly twenty years before 

 1869, the way to success, but had attracted very 

 few followers, so that even our official surveyors 

 did more to retard than to advance this branch 

 of geology, while in regard to metamorphism the 

 wildest ideas were not seldom proclaimed. Light 

 gradually dawned, misconception after miscon- 

 ception was dispelled, until in 1883 Prof. Lap- 

 worth made the great forward step in this branch 

 of the subject by discovering the " Secret of the 

 Highlands." Petrology now claims dozens of 

 students, busily engaged in clearing up the diffi- 

 culties and solving the puzzles of this or that 

 region, and the study of rocks has become as 

 truly scientific as that of palasontology. 



The value of geology for economic purposes has 

 been increasingly recognised during the last fifty 



