MINERALOGICAL GEOLOGY 
405 
accepted opinion. Sea-water from which 37 per cent of its orig¬ 
inal volume must be evaporated before gypsum and borates can 
be precipitated; or 97 per cent of its volume before common 
salt can form could hardly be termed fresh water. The salinity 
is many, many times that of the ocean itself. Bittern lakes is a 
more appropriate name for such inclosed bodies of water. 
In the case under consideration the determination of the exact 
geologic age and origin of the borate beds is of much greater im¬ 
portance than such questions are usually. In the original paper 
one could hardly give this subject the detailed attention that it 
merited, or that the recorded observations warranted. Only the 
main conclusions on these points were formulated; the proofs 
could be well made to fill twice the number of pages that the entire 
paper occupies. As these features were purely geologic in char¬ 
acter they were purposely reserved for presentation in a more 
appropriate place. 
Singularly enough, the exception which Mr. Strong dwells upon 
is the very feature concerning which there was taken particular 
pains to avoid obscurity. The statement that the borate-bearing 
clays are continuous from the Pacific Ocean to Death Valley, and 
that they are mainly marine deposits is amply borne out by the 
fact of the occurrence in them of abundant marine fossils around 
the Mojave Desert. That these beds are the same as the similarly 
appearing clays of Silver Peak district, and farther northward and 
eastward is very questionable. Personal observations, which have 
been rather extensive, indicate clearly that they are not identical. 
Beyond Death Valley to the northeastward some of the yellow 
Tertiaries may be fresh-water deposits at least partly. Quite 
likely some of them are. However, there seemed to be no critical 
evidence demonstrating that such is really the case. 
The quotations from Government reports which Mr. Strong 
relies upon for his main proofs are very far from being convinc¬ 
ing. They rather weaken the force of his exception. Doctor 
Spurr is rightly extremely cautious in all of his statements bearing 
upon this point; he says merely that the Funeral Range beds 
resemble the Silver Peak Tertiaries. The occurrence of a stray 
molluscan shell of fresh-water type, of “grass” remains, and even 
of coal-beds in a sequence of strata a mile in thickness does not 
argue much one way or the other for fresh-water or marine con- 
