Review of Recent Geological Literature. 191 
"sedimentary." All eruptions are produced by the direct operation of 
physical forces. In fact, it would seem that all natural operations must 
be either mechanical or chemical. Otherwise the classification of ore 
deposits presented here is a good, working arrangement, and much bet- 
ter than many that have been proposed. The statement on page 81 that 
"there is no deposit of ore known to be of eruptive origin, which is at 
present worked," is not strictly true. Under "mechanical" ore deposits 
we find only tin, gold and platinum placers as examples, thus excluding 
iron sands and the "recomposed" iron ores of Michigan described by 
Wadsworth and Van Hise. 
The "simplest illustration" of "precipitated deposits" is not clearly 
given (page 82). Bog iron ore is not formed by the transportation of hy- 
drated sesquioxide of iron in solution and its precipitation in the pres- 
ence of certain vegetable acids, but rather by the carrying of carbonates 
and other salts of iron in solution through the aid of these vegetable 
acids and their precipitation as hydrated sesquioxide of iron on being 
oxidized by the atmosphere and oxygenated waters. 
We notice a careless use of the term "boulders" on page 98, where it 
is used to signify the "float" or masses detached from a vein and rolled 
down the hillside. Again, on page 99, the "country rock" is said to be 
"sharply defined," meaning rather the vein or its walls. On page 114 
the term "calcine" is said to mean "to allow ores to decompose in the air 
at ordinary temperatures," which is of course incorrect. The following 
proper names are misspelled: Chamberlin, Andreasberg, Wohler, Lott- 
ner, and Mesabi. 
It is a good idea to teach the student the intimate connection between 
rocks and ore deposits. Our author dwells on the fact that all rocks 
contain ores and that the most probable source of all our valuable min- 
erals is the eruptive rocks. When the reader once realizes that all rocks 
are incipient or potential ore deposits he first perceives the necessity of 
a knowledge of geology in order to be successful in mining. The sec- 
ondary processes which operate to bring about the concentration of 
these disseminated ore-particles are also well described. The all-impor- 
tant agency of circulating waters is occasionally overlooked, however, 
as for instance on page 126, where standing water is said to account for 
the replacement of limestone by iron ore on the Gogebic range. The 
better supposition is that the waters flowed along the pitching trough, 
formed by the intersection of the dikes and the quartzite, and that the 
ore was deposited at the confluence of the ferriferous waters, which had 
percolated down through the ferruginous cherts, with the oxygenated 
waters which came more directly down on top of the quartzite from the 
surface. 
The condition of the Canadian iron mining industry and its future 
prospects are rather facetiously described by the remark that there are 
undoubtedly "great possibilities in store" for the iron industry of 
Canada. 
The iron ores of Cuba are not mentioned, although they are of vastly 
greater importance in this country than the ores of Elba or Spain. The 
