581 
[Shaler. 
Salt deposits are divisible into two groups : in the first of these 
divisions the saline material is held in solution in water which is 
contained in sedimentary beds formed on old sea bottoms. Tn this 
case the presence of salt is attributable to the imprisoning in the 
interstices of the strata of the marine waters in which the beds were 
formed. As T. Sterry Hunt and others have shown, this embedded 
sea water may, under favorable circumstances, remain confined in 
the strata for an indefinite period. The presence of such marine 
waters manifestly affords^no evidence as to the former conditions 
of climate in the time when and in the region where the materials 
were accumulated. The other smaller but economically more im- 
portant group of saliferous deposits consist in the accumulations of 
salt and the other mineral substances contained in waters which 
have been more or less completely evaporated. Such deposits in all 
cases appear in the form of rock salts either in the pure state or 
more or less commingled with other sedimentary materials. It is 
evident that, wherever such accumulations occurred, the climate at 
the time of their formation must have been of a peculiar arid na- 
ture, that is, the measure of evaporation in the given field must 
have considerably exceeded that of the rainfall. 
The various deposits of rock salt are evidently divisible as re- 
gards the circumstances of their formation into two groups to 
which we may give the name of marine lagoon deposits and dead 
sea deposits. The former class of accumulations are found along 
seashores where the neighboring land has a rainfall less than the 
evaporation and where the physical conditions of the shore favor 
the enclosure of considerable areas by coast barriers. From time 
to time the sea waters obtain access to these embayed areas and 
are evaporated to the point where they precipitate their dissolved 
materials. It appears possible, in many cases, to discriminate the 
deposits formed under such circumstances and those accumulated 
in the dead seas. The marine character of the neighboring con- 
temporary sediments, the shape of the basins and perhaps the 
chemical nature of the precipitates may afford data which will en- 
able us to determine the particular conditions of the accumulation, 
and thus to ascertain whether or no it was formed along a sea- 
shore. It appears to me also possible in most cases where the 
physical conditions of the deposits are well revealed to separate 
the dead sea deposits from those which were accumulated along the 
shores. From the general geology of the district it is, in many 
cases, possible to determine in a direct manner whether the accu- 
