NATURE 



241 



THURSDAY, JULY 15, 1897. 



THE ANCIENT VOLCANOES OF BRITAIN 

 The Ancient Volcanoes of Britain. By Sir Archibald 

 Geikie, F.R.S., Director-General of the Geological ! 

 Survey. Vol. I., pp. xxiv. + 477 ; Vol. II., pp. xvi. + 

 492. (London : Macmillan and Co., Ltd., 1897.) 



THE Edinburgh school of geology, when of old it 

 formulated the theory of existing causes of terres- 

 trial change, established the fundamental principle of 

 modern geological science. Thanks to this school, men 

 learnt how rocks were formed, how the strata of the 

 earth's crust were built up, how slow had been the 

 evolution of the continents and oceans, and how im- 

 portant is the conception of time in regard to the past 

 history of the globe. The brilliant representative of 

 this illustrious school who has recently published a 

 history of the volcanoes of Great Britain, sets forth in 

 this remarkable treatise the great features in the volcanic 

 history of the earth, and establishes the principles which 

 will henceforth guide geologists in the study of the 

 massive crystalline rocks. 



From the remotest times there have existed on the 

 surface of the globe volcanoes essentially similar to those 

 now active. Such is the doctrine which Sir Archibald 

 Geikie maintains. He has proved the uniformity of the 

 phenomena and of the volcanic products throughout 

 the geological past. He has indicated the cycles of 

 differentiation among the magmas, and their recurrence 

 in successive ages. He has shown how the sequence 

 and structure of ancient eruptive rocks are to be 

 determined. 



The geological historian who shall hereafter record 

 the stages in the progress of our knowledge regarding 

 what may be termed fossil volcanoes, will attribute their 

 first discovery to Guettard and Desmarest ; their analysis 

 to Sorby, to the German petrographers, and to Fouque 

 and Michel L^vy (to whom the present work is dedi- 

 cated) ; and their synthesis to Sir Archibald Geikie, who 

 has resuscitated and reconstructed the old dismantled 

 volcanoes, buried under the geological formations of 

 Great Britain. 



The author, in a preface dealing with the history of 

 discovery in the domain of volcanic geology, introduces 

 his subject in the following sentences. 



" In no department of science is the slow and 

 chequered progress of investigation more conspicuous 

 than in that branch of geology which treats of volcanoes. 

 Although, from the earliest dawn of history, men had 

 been familiar with the stupendous events of volcanic 

 eruptions, they were singularly slow in recognising these 

 phenomena as definite and important parts of the natural 

 history of the earth. Even within the present century, 

 the dominant geological school in Europe taught that 

 volcanoes were mere accidents. A juster appreciation 

 of the nature of the earth's interior was needed, before 

 men could recognise that volcanic action had once been 

 vigorous and prolonged in many countries, where no 

 remains of volcanoes can now be seen." 



"To France, belongs the merit of having laid the 

 foundations of the systematic study of ancient volcanoes. 

 As far back as the year 1752, Guettard recognised that 

 the Puys of Auvergne were volcanic cones that had 

 poured forth streams of lava. But it was reserved to 



NO. 1446, VOL. 56] 



Desmarest twelve years later to examine the question 

 in detail, and to establish the investigation of former 

 volcanic action upon a broad and firm basis of careful 

 observation and sagacious inference. He discovered 

 that the volcanoes of Central France were not all of one 

 age, but had made their appearance in a long series, 

 whereof the individual members became less perfect and 

 distinct in proportion to their antiquity." " While these 

 fruitful researches were in progress in France, others of 

 hardly less moment were advancing in Scotland. Hutton, 

 as a part of his immortal 'Theory of the Earth,' had 

 conceived the idea that much molten material had been 

 injected from below into the terrestrial crust, and he 

 had found many proofs of such intrusion among the 

 rocks of his native country. His observations, confirmed 

 and extended by Playfair and Hall, and subsequently by 

 Macculloch, opened up the investigation of the sub- 

 terranean phases of ancient volcanic action" (Preface, 

 pp. vii.-viii.). 



From the peculiarly favourable structure of the 

 country, Britain has been enabled to make many im- 

 portant contributions to the investigation of the subject. 

 De la Beche, Murchison and Sedgwick led the way in 

 recognising, even among the most ancient stratified forma- 

 tions of England and Wales, the records of contempo- 

 raneous volcanoes and their subterranean intrusions. 



A new stage in the history of volcanic geology was 

 entered when Sorby introduced the method of micro- 

 scopic examination of rocks by means of thin slices. 

 Petrpgraphical investigation was thereby enabled to 

 keep pace with stratigraphical research. The rocks of 

 the whole globe have been made to pass through the 

 German laboratories, and thus precise knowledge has 

 been obtained regarding the mineralogical composition 

 and structure of the rocks, and light has been thrown on 

 the true principles of their classification. In France, 

 Fouque and Michel Levy, studying volcanic rocks both 

 in the field and in thin sections, have been able to repro- 

 duce the principal types artificially m their laboratory. 



In Sir Archibald Geikie's volumes the study of 

 ancient volcanic rocks now emerges from the laboratory, 

 and is prosecuted under the broad sky among the crags, 

 the shores, and the isles. Not that the minute descrip- 

 tion of internal structure or of chemical and mineral- 

 ogical composition is neglected by him ; but the rocks 

 are no longer looked at as they are in themselves : their 

 chief value is now sought in their association as parts of 

 a connected volcanic history. A dyke is only noticed 

 when its description allows it to be connected on the one 

 side with a subterranean reservoir, and on the other with 

 its superficial display of lavas or fragmental discharges. 

 The rocks are studied as much from the point of view of 

 their origin as from that of their composition, and their 

 structure is shown to be in relation to some determinate 

 part of a volcanic group. All that has been done, all 

 that has been said in regard to these questions, will be 

 found summed up in Sir Archibald's work, while his 

 masterly exposition of the history of volcanoes from the 

 earliest times down to our own day is enhanced with 

 ingenious conclusions respecting the nature and causes 

 of volcanic action. 



The fossil volcanoes reveal no craters. No trace of 

 their original cones has survived to our time, save in 

 some exceptional cases where they have been en- 

 tombed under lavas, or have been preserved under other 

 accumulations. These and other characteristics con- 



