Reviews — Sutton's Theory of the Earth. 321 



various rocks (some of them crystalline, others sedimentary, but 

 occasionally including water-worn boulders of the former) — i.e., 

 a result of shattering explosions, followed by solfataric action. 

 Hence the name Kiraberlite must disappear from the list of the 

 peridotites, and even from petrological literature, unless it be 

 retained for this remarkable type of breccia. 



Boulders, such as we have described, might be expected to occur 

 at the base of the sedimentary series, in proximity to a crystalline 

 floor. The Karoo beds in South Africa, as is well known, are 

 underlain in many places by a coarse conglomerate of considerable 

 thickness and great extent, called the Dwyka conglomerate, which 

 is supposed to be Permian or Permo-Carboniferous in age. It crops 

 out from beneath the Karoo beds at no great distance from the 

 diamond-bearing district, and very probably extends beneath it. 

 If this deposit has supplied the boulders, the date of the genesis 

 of the diamond is carried back, at the very least, to Palaeozoic ages, 

 and possibly to a still earlier era in the earth's history. 



S, E "V^IIB "W S. 



I. — Theoky of the Earth, with Proofs and Illustrations. In 

 Four Parts. By James Hutton, M.D., F.E.S.E. Vol. Ill, 

 Edited by Sir Archibald Geikie, D.C.L., F.R.S. 8vo ; pp. xvi, 

 278, with Index to Vols. I and II. London, 1899. Published by 

 the Geological Society, Burlington House, London. Price 3s. 6d. 



IN the annals of Geology, Hutton's "Theory of the Earth" ranks 

 as one of the principal classics, and if this original work has 

 been to some extent eclipsed by Playfair's lucid "Illustrations" of 

 it, the fame of the author and his intluence on the progress of 

 geology have thereby been greatly enhanced. Of the four parts 

 which the "Theory of the Earth" was planned to comprise, two 

 only were published (in separate volumes) in Edinburgh in 1795, 

 two years before the death of the author. An incomplete MS. of 

 tlie third volume, intended to embrace the third and fourth i^arts 

 of the work, has long been in the possession of the Geological Society. 

 This MS. commences with Chapter IV; the efforts to discover the 

 earlier portion having proved unsuccessful. It is remarked bj^ the 

 Editor that altlumgh there is reason to believe that the MS. of 

 Vol. Ill was nearly ready for the printer at the time when the other 

 two volumes were joublished, yet it is possible that the want of 

 drawings to illustrate the text may have caused the delay. The six 

 chapters now published deal mainly with Hutton's views regarding 

 the origin of granite; they include narratives of his excursions into 

 different parts of Scotland, notably to Glen Tilt, to Galloway, and 

 to the Isle of Arran. As the Editor points out, Hutton's Essay 

 on Arran " is a masterpiece of acute observation and luminous 

 genei'alization. Had it been published in liis lifetime, it would 

 have placed him at once as high in the ranks of field-geologists as 



DECADE IT. VOL. VI. NO. YII. 21 



