Jien'eics — Crane's Treatise on Oold and Silver. 35 



side of the calc-sericite schist of Central Perthshire, is also included in 

 this zone. The metamorphism of these rocks increases along the 

 course of their outcrop from Ardrishaig to the head of Loch Fyne, 

 as shown by J. B. Hill. In the Upper Arenaceous zone the author 

 would now include only the Central Highland quartzite, transferring 

 the Blair Atholl limestone to the top of his Upper Argillaceous zone. 

 He adopts Cunningham-Craig's conclusions for the Blair Atholl district 

 that there is an upward succession from the Ben Lawers schist, 

 through black graphitic schist and Blair Atholl limestone into 

 quartzite. Ho also accepts the view that there was a period of 

 local ei'osion at the base of the quartzite, when the boulder-bed 

 of Schichallion and Islay was laid down. The Moine gneisses are 

 classed with the quartzite in the Upper Arenaceous zone in the text, 

 but in the tabular statement (p. 96) they are kept outside it and 

 marked as of vincertain position. The author's acquaintance with 

 these rocks must be slight. He adduces "their peculiar granulitic 

 structure " as evidence of their sedimentary origin. 



The age of the Highland schists cannot at present be determined. 

 Pebbles of these rocks occur abundantly in the conglomerates of 

 Lower Old Red Sandstone age, and they are also found in certain 

 conglomerates of the Upper Siliirian of the south of Scotland, but 

 how much older they may be it is impossible to say. However, 

 developing in a later chapter a theory to account for the structure of 

 the Grampians, the author takes it that the sediments which ultimately 

 formed the Highland schists were laid down in a sinking geosynclinal 

 in the old continent of Archaean gneiss. And in the final chapter of 

 the work we read that the first denudation of the upheaved Highland 

 chain began with the deposition of the Torridon Sandstone, and was 

 continued through Cambrian times. It is evident, thei*efore, that the 

 author opines that the Highland schists belong to some formation 

 intermediate in age between the Archsean gneiss and the Torridon 

 Sandstones, but this is little more than a guess. 



{To he continued.) 



II. — A Tkeatise on Gold and Silvj^r. By Walter Crane, Ph.D. 

 pp. 727 -|- X, with 20 illustrations and 9 plates. New York, 

 John Wiley & Sons ; London, Chapman & Hall, 1908. Price 

 21s. net. 



WE learn from the preface that the Carnegie Institution of 

 Washington has in hand an Economic History of the United 

 States. Dr. Crane's elaborate treatise is the first instalment of that 

 •work, and is eloquent testimony to the comprehensiveness of the 

 scale upon which it has been planned. The author has evidently 

 spared no pains to make this history of the mining of gold and silver 

 in the United States as complete and exhaustive as possible. 

 Extensive quotations are introduced from original papers, particularly 

 in the chapters dealing with the occurrence and association of gold 

 and silver and their geological distribution, and references are in 

 all cases given to enable the reader, who so desires, to look up the 

 original sources. By giving the actual words of a writer the 



