230 Revieics — Prof. Cole's Practical Geology. 



VIL— Aids in Practical Geology. By Prof. Grenyille A. J, 

 Cole, F.G.S. 8vo. pp. 402. (London, Charles Griffin & Co., 1891.) 



PROFESSOE Grenville Cole's " Aids " is a work occupying an 

 unique position in geological literature. Every one trained in 

 the modern school of Geology has a vivid recollection of the number- 

 less sources from which he was compelled to select the various 

 necessary items of information. Apart from ordinary geological 

 text-books, there were works on chemical analysis, qualitative and 

 quantitative, on blowpipe analysis, mineralogy, and general physics, 

 technical treatises and memoirs on the microscopical examination of 

 rocks, and various other less important references too numerous to 

 mention. He was continually dependent upon the Professor for 

 advice and help ; and he was led most emphatically to realize the 

 extraordinary combination of scientific methods that is requisite for 

 the satisfactory study of a geological formation. The new volume 

 before us dispels all these difficulties, and now, for the first time, 

 renders it possible even for an ordinary amateur to gain an adequate 

 knowledge of the subject up to date. Not only is this the case, but 

 many of the open paths for further investigation are incidentally 

 pointed out, with sufficient references to original memoirs to enable 

 an enthusiastic student to proceed far in this direction. 



Prof. Cole is throughout eminently practical. Several guides to 

 the beginner in Field Geology have already appeared, but we have 

 never met with so concise a series of useful hints as to small matters 

 that most geologists have to learn by experience, as can be found in 

 the first part of the present work. Not only is the equipment dis- 

 cussed in a manner that betokens wide experience, but the most 

 precise information is afforded as to the best form of gymnastics for 

 various difficult circumstances, such as the crossing of streams and 

 the scaling of crags. In the remarks on packing specimens, again, 

 even such minutise as the peculiar Parcel Post regulations of Italy 

 are briefly noticed ; and in this section of the book, as in the others, 

 scarcely an instrument is mentioned without some allusion to its 

 cost, its comparative efficiency, and the name of the maker from 

 ■whom it can be obtained. In many instances, directions are given 

 for the construction of simple apparatus from common materials, 

 such as gallipots, corks, and wire ; and the circumstances of travellers 

 in regions distant from ordinary civilization are always carefully 

 remembered. 



The second part of the book is devoted to the examination of 

 minerals, forming not merely a concise statement of the ordinary 

 methods of determinative mineralogy and an index to the characters 

 of the species of most common occurrence, but also comprising 

 numerous hints and cautions which the student will soon learn to 

 appreciate. Two conspicuous features are the elaborate treatment of 

 the determination of specific gravities, and an interesting chapter on 

 Szabo's method of quantitative flame-reactions for the felspars and 

 their allies. After these preliminaries, the most important part of 

 the work, relating to the examination of rocks, immediately follows. 

 Eock-structures are first treated in a general way, the principal 



