Marcou’s Geology of the United Staies. 325 
n open to the criticisms. 
IIT. Mounrarn Sysrems.—The author describes the mountain 
ystems of North America and their they 
must be according to the theoretical views of Elie de umont. 
determination of the age and relations of each by means of 
observed facts would be positive knowledge and of some service 
to the science. 
IV. Reszarcues.—The points in the explorations of the au- 
thor which give his work special prominence, are the assumed 
regrgice pe ge =: 
.) of Triassic rocks in the Lake Superior region ; 
(2.) of the Permian Formation over the slopes of the Rocky 
Ountains ; | : 
(3.) of Triassic rocks in the same Rocky Mountain regions ; 
(4.) of Jurassic rocks, in the same region. 
_ We should take pleasure in claiming for the author the estab- 
lishment of either one or all these points, if we could justly 
* Mr. Mareou says, with characteristic self-complacency, and with evident irri- 
ol . r 
