NATURE 



25 



THURSDAY, NOVEMBER 9, 1899. 



THE GEOLOGY OF THE SOUTHERN 

 UPLANDS OF SCOTLAND. 

 The Silurian Rocks of Britain. Vol. I. Scotland. By 

 B. N. Peach, F.R S., and J. Home, F.R.S.E. ; with 

 Petrological Chapters and Notes by J. J, H, Teall, 

 M.A., F.R.S. Pp. xviii + 749; plates xxvii, and a 

 coloured map. (Memoirs of the Geological Survey of 

 the United Kingdom, 1899.) 

 T^HE student of historical geology, in his endeavour to 

 -*- obtain a comprehensive view of the sequence of 

 events in a particular area, is too frequently conscious 

 that he is gazing at a distorted picture. It is probably 

 beyond the power of any one person to gather together 

 the tangled mass of detail, and by a process of anamor- 

 phosis, to illustrate the geology of even a single country 

 in such a manner that while the proportions of the whole 

 work are harmonious, every important detail is also pre- 

 sented with conspicuous clearness. But that which is 

 too much for one person may be carried out by a band 

 of workers under the direction of one chief; and 

 fortunately we in Britain, the mother-country of strati- 

 graphical geology, not only possess this band, but 

 know that it is actually engaged in the accomplishment 

 of the desired work. 



It is now some years since the first volume of a series 

 of memoirs devoted to a detailed study of the various 

 great groups of the British stratigraphical rock-column 

 was issued by H.M. Geological Survey. This series, 

 when complete, will place within reach of the geologist 

 a history of the British strata, of which we cannot over- 

 estimate the value. The Jurassic rocks of Britain have 

 already been described in two volumes : one, by Mr. 

 Fox-Strangways, treating of the Jurassic rocks of York- 

 shire ; the other, by Mr. H. B. Woodward, describing 

 those of the other British areas. Another volume, by 

 Mr. Clement Reid, is devoted to the Pliocene strata, and 

 we are now presented with the first volume of the series 

 in which the British Silurian rocks will be described, the 

 particular volume under consideration containing an 

 account of the Silurian rocks of Scotland. 



The most important area of Silurian rocks in Scotland 

 is de\eloped in the Southern Uplands, and to consider- 

 ation of this area the present volume is essentially con- 

 fined. It is noted, however, that igneous rocks and 

 radiolarian cherts have been detected along the southern 

 border of the Eastern Highlands ; and in this connection 

 it is interesting to note that Hugh Miller in his 

 " Rambles of a Geologist " records, on the authority of 

 Dr. Emslie, the occurrence of graptolites in a slate 

 quarry at Gamrie Head, near Banff. 



In glancing at the memoir by Messrs. Peach, Home 

 and Teall, we are at once struck with the fact that the 

 great bulk of the contents consists of records of fresh 

 observations. The amount of work which the authors 

 have performed in the field and the laboratory is sur- 

 prising even to the general reader, still more so to any 

 one who from some knowledge of the area is cognisant 

 of its extraordinary complexity. 



Great as the amount of new work recorded in this volume 

 NO. 1567, VOL. 61] 



undoubtedly is, the authors took up their study of the 

 region subsequently to jts description by a number of 

 other geologists, of whom the illustrious Hutton was the 

 first, while Prof. Lapworth, as is well known, reduced the 

 stratigraphy of the area to order in several masterly 

 papers appearing in the Quarterly Journal of the 

 Geological Society, the Geological Magazine, and the 

 Annals and Magazine of Natural History. The im- 

 portance of Prof. Lapworth's work is acknowledged m 

 the volume under notice, in the fullest manner, both in 

 the chapter devoted to the history of previous researches 

 in the south of Scotland and in those which treat of the 

 geology of the region in detail. 



Though Lapworth led the way to appreciation of the com- 

 plicated nature of the geology, the authors of the memoir 

 have not only verified his conclusions, but added a great 

 deal of confirmatory matter, and have furthermore made 

 a series of discoveries which throw light upon questions 

 of prime importance to geologists. 



.\mong the discoveries which are of general interest 

 as shedding light upon geological matters of widespread 

 importance, we may notice the discovery of Arenig 

 graptolitic mudstones, radiolarian cherts and contem- 

 poraneous volcanic rocks over very wide tracts of country 

 in the Southern Uplands and South-eastern Highlands ; 

 the detection of the occurrence of further volcanic out- 

 bursts in Llandeilo and Caradoc times ; the evidences of 

 the lateral variations in the sediments of different ages 

 indicating a source of supply of terrigenous sediment to 

 the north-west of the area, and of the gradual encroach- 

 ment of the coarser sediments to the south-east, in the 

 later periods of Silurian times ; the definition of a Down- 

 tonian period between Ludlow and Old Red Sandstone 

 times, and the description of the rocks of this period ; 

 and the discovery of a remarkable fauna of fishes in 

 these Downtonian strata, which has been described by 

 Dr. Traquair. The above discoveries are mainly due to 

 Messrs. Peach and Home, who, like Lapworth, have 

 chiefly utilised the graptolites as a means of comparing 

 the strata of different localities, though they have also 

 obtained much assistance from the persistent cherts, 

 which, as shown many years ago by Dr. G. J. Hinde, 

 were largely formed by the accumulation of tests of 

 radiolaria. The writers appear to adopt the suggestion 

 that these radiolarian cherts are deep-water deposits, 

 though, in consideration of the evidence which they 

 adduce in support of the existence of a tract of land at 

 no great distance to the north-west, it seems doubtful 

 whether the cherts are strictly comparable with the 

 abyssal radiolarian oozes of modern oceans. Mr. Teall 

 gives a petrographical account of the remarkable volcanic 

 rocks associated with the radiolarian cherts, and of the 

 contemporaneous volcanic rocks of higher strata ; also 

 a description of the intrusive rocks of the Girvan and 

 Galloway district, with details of the nature of the 

 metamorphism impressed upon the rocks surrounding the 

 irruptive igneous masses. One exceedingly significant 

 suggestion is made to the effect that the coarsely crystal- 

 line plutonic rocks were consolidated beneath a small 

 thickness of overlying rock- cover, though it is stated 

 that the evidence for this is imperfect. 

 The results of the palseontological investigations are 



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