Reviews—Metals 1n Pre-Cambrian of Ontario. 578 
V.—Merattoeeneric Epocus 1n THE PRe-CamBrian oF Ontario. By 
W. G. Minter and C. W. Kyieur. Trans. Roy. Soc. Canada, 
ser. ul, vol. ix, pp. 241-9, 1915. 
HE enormous economic importance of the ore bodies of Ontario 
has enabled geologists to study the Pre-Cambrian rocks there 
disclosed with very special intimacy. While only a few years ago 
Lindgren found it advisable to consider the Pre-Cambrian era of 
ore deposition as a whole, the authors of the paper before us have 
distinguished four major epochs of metallogenesis. The following 
table summarizes the main conclusions :— : 
Keweenawan.—Basic intrusions passing in places into acid rocks. 
1. Silver, cobalt, nickel, and arsenic at Cobalt. 
2. Nickel and copper at Sudbury. 
3. Gold deposits (not now productive). 
Animikean.—Chemical deposition of ‘iron formations ’. 
Algoman.—Intrusions of granite. 
1. Gold at Porcupine and many other localities. 
2. Galena, zincblende, and fluorspar. 
Basic intrusions of post-Timiskamian age. 
1. Nickel and chromite. 
2. Magnetite and titaniferous magnetite. 
Timiskamian.—Chemical deposition of ‘iron formations’ (of minor 
importance). 
Laurentian.—Intrusions of granite (which probably gave rise to 
ore deposits since removed by excessive erosion). 
Grenville.—Chemical deposition of ‘iron formations’. 
Keewatin.—Extrusions of basic volcanic rocks. 
The table brings out the importance of igneous activity in the 
formation of ore deposits, the succession including three cycles of 
intrusion each beginning with basic and concluding with acid rocks. 
At present the ‘iron formations’ of Animikean and Timiskamian 
-age.in Ontario are not productive, but in Michigan they are the 
annual source of millions of tons of iron-ore. 
AGSHC 
VI.—GuiIpE-B00K oF THE WestERN Unitep States. Part C: Tue 
Santa Fe Rovre. Bull. 613 U.S.G.S. pp. 194. Washington, 
1915. 
({X\HIS book, which is one of a series of four dealing with the main 
railway routes in the western United States, is issued with 
a view to furthering the ‘‘ see America first”? movement, by providing 
a handy book which will give the traveller all the important features, 
both geological and geographical, in order, as he journeys along the 
railway. The book is divided up into sections, each with its own 
map showing the railway and the country from ten to fifteen miles 
on either side of it, with contours and geological boundaries. Each 
section covers about sixty miles, the whole route stretching from 
Kansas City to Los Angeles, and including a journey to the Grand 
