594 Wiz JKOUUINCAUIL, (OME GIR OIG VZ 
ate discussion, but the map recognizes that the ore deposits are of 
different ages and the context makes the hypothesis applicable to 
deposits of other ages. Of course changes in the courses of the cur- 
rents, changes in the areas of derivation, and in those of deposition 
must be taken into consideration in explaining the later deposits. If 
the hypothesis urged by Chamberlin is good at all, it is applicable to 
all ages, because there must always have been different degrees of 
enrichment of the oceanic waters in different parts corresponding to the 
different amounts of metalliferous material brought in from the land 
and this must have been carried in the direction of prevailing currents. 
If the inequalities of the sea bottom tended to concentrate metallifer- 
ous deposits at one age they should do so at others under similar con- 
ditions. Mr. Winslow lays much emphasis upon the degradation of the 
formations whereby the disseminated metals were removed from their 
original matrix and brought together in the crevices or cavities in 
which the ores were accumulated. He justly points out the distinction 
between this and the narrow views of lateral secretion against which 
some authors have argued. Perhaps on his own part he is not wholly 
beyond criticism in the same direction in his interpretation of the 
views of Whitney and Chamberlin which are scarcely distinguishable 
from his own in this particular. The ideal diagram on page 548 of 
The Ore Deposits of Southwestern Wisconsin, Vol. 1V., Geology of Wis- 
consin, very sharply emphasizes the function of surface decomposition, 
conjoined with concentration and segregation below. But this is 
rather a matter of nice toning and shading of opinion than of impor- 
tant distinctions. ‘The report is much to be commended for its great 
array of facts which will form a memorable contribution to the science 
of ore deposits. Mr. Winslow has prepared a list of errata which he 
will gladly send to any desiring it. rs Cues 
Elementary Paleontology for Geological Students. By Henry Woops, 
B.A., F.G.S. [Cambridge University Press. Macmillan & 
Oxy Na Wo] 
This book wili supply a want felt in all colleges where historical 
geology or paleontology is taught. It is something that has been 
lacking in the English literature on this subject. Though we have 
great paleontologists and have in our libraries numerous large and 
well written works on paleontology in various foreign languages and 
