Reviews — GeiJde's Ancient Volcanoes of Great Britain. 371 



diamond. Moreover, microscopic diamonds have been found in 

 meteoric irons. Yet it must be regarded as a singular circumstance 

 that basalts far richer in iron than the Kimberley diamond-rock 

 have passed through beds containing carbonaceous matter, and 

 contain large masses of metallic iron which is not associated with 

 diamond either at Kimberley or elsewhere. 



It must be a matter of regret to geologists, and indeed to all men 

 of science, that Professor Lewis was not spared to continue his 

 investigations on a subject which presents so many points of interest. 



11, — The Ancient Volcanoes of Great Britain. By Sir Archibald 

 Geikie, F.R.S., D.C.L., D.Sc, etc., Director-General of the 

 Geological Survey. Imperial 8vo. In two volumes. Vol. I, 

 pp. xxiv and 477, with four maps and 175 illustrations. Vol. II, 

 pp. xvi and 492, with three maps and 382 illustrations. 

 (London: Macmillan & Co., Ltd., 1897. Price 36s. nett.) 

 (Second notice.) 

 (WITH PLATES XVI AND XVII.) 



ALTHOUGH we have no " burning mountains " in England, and 

 no evidence of volcanic action but such as belong to the 

 remote past, yet a careful study of modern volcanoes and of the 

 products of eruptions observed all over the world, has given us 

 the key by which to interpret the ancient tuffs, lavas, basalts, 

 gabbros, andesites (porphy rites), trachytes, pitchstones, felsites, 

 rhyolites, etc., which are met with in these Islands, and also to 

 detect the old plateaux discharges of volcanic materials of Car- 

 boniferous age that now form broad tablelands or ranges of hills ; 

 or the puys, whose ejected materials formed cinder-cones or 

 lava-domes and were confined to smaller areas round the centres 

 of eruption, with occasional flows of basic lava, as admirably dis- 

 played in Central France. To these must be added the innumerable 

 examples of dykes, volcanic necks, bosses, and sills, exposed by 

 denudation, all of which have been carefully studied and classified. 



With the ordinary type of modern, and especially of active, 

 volcanoes, we need not here concern ourselves. The lofty cones 

 of the Vesuvian type, with their widespread lavas and ashes, their 

 vast craters, and numerous parasitic vents, can form no lasting 

 record of volcanic action. Subaerial denudation, acting incessantly 

 year after year, gradually planes down and carries away their 

 unstable slopes, and if unchecked by any fresh discharge of volcanic 

 material, degradation will at last have removed the whole cone. 

 But whilst no universal rule can be laid down as to the relative 

 durability of any rock, yet in the course of vast periods of time 

 during which denudation and disintegration have been carrying on 

 their destructive work, the older eruptive masses, consisting usually 

 of the more durable materials, have at last risen into prominence, 

 and now form some of our wildest scenery and the summits of 

 our most craggy and spiry mountains. Among the many examples 

 given, we cannot forbear to quote one illustration from the chapter 

 entitled the "Influence of Volcanic Eocks on the Scenery of the 

 Land," which is in Sir A. Geikie's most agreeable style — 



