Reviews — Lieut.- Colonel Sorsbie — Geology for Engineer*. 231 



a brief account of the history of coal, and, as the author remarks, 

 it is not a mineral but a rock. Using the term in a popular sense he 

 includes " Anthracite, the Humic or so-called Bituminous coals, the 

 Sapropelic coals, which include the Cannels and Bogheads, the Brown 

 coals, Lignites, and Peat". Their chemical properties, physical 

 characters, and stratigraphical positions are duly pointed out, and 

 the author then deals with the origin of peat, lignite, and the several 

 varieties of coal, especially those of Carboniferous age. That there 

 was an excessive amount of carbon dioxide in the atmosphere of the 

 "-Carboniferous period is regarded as extremely doubtful. The " Peat- 

 to- Anthracite theory " is rejected. Carboniferous coals were formed 

 quickly, and although in the initial stage they may have resembled 

 peaty deposits they did not necessarily pass through the stages of 

 lignite, etc. Both peat and coal have been formed under a variety 

 of circumstances, and the theories of ' growth-in-situ ' and 'drift', 

 as applied to coal, may be equally true. It is shown how coal 

 may be formed under very different circumstances and from very 

 diverse materials. Biochemical changes in plant debris were brought 

 about by bacteria, and the author is led "to attribute a considerable 

 share in the coal building of the Humic, Sapropelic, and Anthracitic 

 types to regional, if not thermal, metamorphism ". 



As a companion volume of small dimensions, we may commend 

 No. 21 of Gowan's Nature Books, 1909, price 6d. net, entitled Fossil 

 Plants, and comprising sixty excellent photographs illustrating the 

 flora of the Coal-measures, with explanatory notes, by Mr. Arber. 



IV. — Geology for Engineers. By Lieut. -Colonel R. F. Sorsbie, R.E. 



pp. xxvii, 423, with 94 text-illustrations. London : Charles 



Griffin & Co., 1911. Price 10s. 6d. net. 

 rpHIS is a conscientious attempt to place before engineers all the 

 1_ geological information that may concern their professional 

 undertakings. About half of the volume is taken up with the 

 matter of an ordinary textbook of Geology : with Dynamic and 

 Structural Geology, with Minerals, Mineral Chemistry, Crystallography, 

 Rock-forming Minerals, and Piocks, and with Stratigraphy and 

 Palse ontology. There are illustrations of some of the commoner 

 invertebrate fossils, brief descriptions of both invertebrata and 

 vertebrata, and of the ranges in time of some prominent forms. 

 A general account is given of the geological systems in Britain, and 

 references are made to the occurrence of equivalent formations in 

 various parts of the world. Here the information, though evidently 

 sought out with care, is in some respects seriously behind the times. 

 The tables of strata in North America, Australia, New Zealand, and 

 South Africa are taken from Prestwich's Geology, vol. ii, 1888. 

 Thus it comes to pass that the Acadian and Georgian (Middle and 

 Lower Cambrian) are misplaced and grouped with Primordial under 

 "Lower Silurian", while the Oriskany and Helderberg Beds, now 

 grouped with the Devonian, are placed in Upper Silurian. Eozoon 

 eanadense, moreover, is recorded as a "problematic fossil". Eor these 

 and many other statements the author refers to his authorities, 



