322 Revieics — Dr. W. Gihsou — Geologij of Coal and Coal-mining. 



"the study of Oolite waters leads to the general conclusion that the 

 uncovered beds of limestone yield calcareous waters of a hard character, 

 while the deep beds, and especially the beds covered by clay, yield 

 saline or alkaline supplies." To a certain extent this rule holds good 

 even in such a homogeneous formation as the Chalk, and may be 

 explained on the principle that the higher and more exposed beds 

 receive a larger charge of carbonic acid: where this does not penetrate, 

 the carbonate of lime is not dissolved. The source of such large 

 quantities of a saline matter is probably the stagnant condition of the 

 waters in the hydrostatic basin, which require bleeding by springs or 

 else by continuous pumping, which latter process might be prolonged 

 indefinitely. 



AV. H. H. 



IV. — The Geologt of Coal and Coal-minixg. By Walcot Gibson, 

 D.Sc, r.G.S. pp. X, 341, with 8 plates and 16 text-illustrations. 

 London : Edward Arnold, 1908. Price Is. 6d. net. 



rpHE present volume is the first of a series on Economic Geology, to 

 _L be issued under the general editorship of Dr. J. E. Marr, who 

 remarks that the subject is " yearly receiving more attention in our 

 great educational centres." This is gratifying, as the practical 

 applications of knowledge must ever be one of the aims of those 

 scientific workers who have at heart the welfare of mankind. 



To instruct the mining student, the prospector, surveyor, and mine- 

 manager on those questions which afi'ect the occurrence of coal, is the 

 main object of the book before us, and it is happily written by a 

 geologist who has had a large experience in problems of coal and coal- 

 mining, and who has spared no pains in the preparation of liis work. 



The publication comes at an opportune time, when, owing to the 

 vast amount of coal that has already been raised from our principal 

 coalfields, deeper sinkings in some of them and trial borings in 

 unproved areas on their margins become more and more necessary. 



Here, as pointed out by Dr. Gibson, intimate knowledge of the 

 structure of each coalfield, and of the strata composing the coal- 

 measures, is of t])e utmost importance. In many regions there are 

 considerable thicknesses of red rocks that overlie the productive 

 measures, in some cases conformably, in others with great discordance. 

 The discrimination between these has not yet been satisfactorily made 

 in all areas on our geological maps. 



Moreover, the days are not over when black shales or lignite tempt 

 the ignorant to fruitless enterprise, and we have known a deep and 

 useless boring made in red rocks in an unpromising area, because it was 

 thought from coal being worked under red rocks at Bristol it would be 

 met with elsewhere under similar rocks at no great depth. 



The information acquired in recent years of the horizons marked by 

 certain fossil plants, mollusca, fishes and other organic remains has 

 proved to be of considerable importance, at any rate locally. Thus 

 a knowledge of the succession of rock-types in conjunction with the 

 evidence of the fossils is of signal service in determining horizons in 

 trial borings outside the exposed limits of a coalfield. 



