1/2 The American Geologist. March, iixti. 
considerable quantities of salt. With the next ingress of the 
sea a fresh supply of salt would be introduced in solution, to 
be deposited in the same manner during the next period of 
suspended inter-communication. Such conditions, continued 
over a long period, have resulted in the deposition of the con- 
siderable bodies of salt now found in and about these lakes. 
In the manner just described series of salt lakes were 
formed and may still be seen occupying slight depressions over 
the bottoms of all the abandoned water courses of Patagonia ; 
while every stage in the process of the formation of such lakes 
may be observed in and about the heads of the different inlets 
all along the coast. Exceptional advantages for studying the 
origin of these salt lakes are offered at the head of the bay of 
San Julian and in the valley extending from the bay into the 
interior for a distance of loo miles. In the bottom of this val- 
ley are numerous salt lakes, while in the region about the head 
of the bay there is a succession of lakes and inlets, showing 
every stage in the process of lake formation as detailed in the 
foregoing lines. 
Dr, Otto Nordenskjokl has taken exception to this theory 
of the origin of these salt lakes, holding that they are not resi- 
dual lakes, and that the salt has not been derived directly from 
the sea as I have maintained. He holds that the salinity of 
these lakes is due to the fact that they have no outlets and that 
the salt has been derived, as in many other salt lakes in other 
countries, from the surrounding rocks by the tributary waters. 
To my mind there are two very conclusive arguments against 
this theory and in favor of that of considering these as residual 
lakes. First: — None of these lakes are fed by perennial 
streams, their supply of water being almost entirely limited to 
freshets due to occasional heavy showers, and to melting snow 
in the immediate vicinity, so that it is entirely made up of sur- 
face water and necessarily contains very little, if any, saline 
material. Second: — Those lakes found nearest the coast and 
whose connection with the sea has only just recently been 
completely closed, are found to contain quite as important salt 
deposits as others situated many miles inland where the connec- 
tion with the sea has long been severed ; thus showing that the 
amount of salt in the latter has not been appreciably increased 
during the long period that has elapsed since their final sever- 
