404 
MINERALOGICAL GEOLOGY 
one of long practice. This is the very idea floridly advanced by 
Whitney at the beginning of the geological exploration of the Far 
West. It is a notion which prevails almost unchanged to the 
present day. Yet, the formations carrying the borate mineral are 
only a few of those of the region which are commonly denomin¬ 
ated as “lake beds.” It is mainly because of the fact that the 
notion has been allowed to go so long unchallenged that recently 
so much emphasis is laid upon the marine nature of some of these 
so-called typical lake beds. Stressing this feature somewhat too 
strongly perhaps, some writers seem to have missed the real per- 
port of the argument, and gratuitously infer that it is a plea for a 
marine origin of the borate beds themselves. This conclusion is 
not to be drawn from the memoir in question. 
Nevertheless it is a timely question Mr. Strong recently raises 
in regard to the geologic occurrence of borate deposits. From 
the viewpoint of the prospector, as well as that of the mine oper¬ 
ator, the exceptions to my statements concerning the marine nature 
of the sedimental succession and the possible origin of the borate 
beds that he takes is a fundamental one. The evidences which he 
sets forth and his quotations from other authors all seem to be 
given in support of his opinion that the borate deposits are of 
fresh-water origin, as opposed to my suggestion that some of the 
Tertiaries containing the beds under consideration are without 
question strictly marine in character. It is well known that nearly 
all of the literature on the Tertic deposits of western America 
regards them as laid down in fresh-water lakes. Indeed, it is 
the habit to term them “fresh-water Tertiaries.” There is 
really very little foundation for this assumption. All the later 
and critical data show conclusively that many, if not most, of these 
deposits were not formed in fresh-water at all; and some of them 
are not even water-laid deposits. 
It is hardly to be regarded that Mr. Strong intended to have his 
exceptions taken too literally. The basic idea which he possibly 
meant to convey is that the basins in which the borates were laid 
down were originally fresh-water lakes, or at least land-locked 
bodies of water, in contradistinction to their being once arms of 
the Pacific Ocean. That any of the formations carrying exten¬ 
sive beds of boracite, colemanite, anhydrite, gypsum and rock-salt 
should be laid down in fresh water seems hardly consistent with 
