1 882.] Geology and Paleontology. 923 



well defined as rights and lefts, their straddle is unusually wide. 

 He thought they might have been made by a human foot en- 

 closed in a rawhide sandal much larger externally than the foot. 

 This would at first make a flat track until soaked through, after 

 which it would leave a round impression, but no toe marks. If 

 not by man the tracks could only be made by some clumsy plan- 

 tigrade quadruped like a bear or a gigantic ground sloth, My- 

 lodon. such as lived in the Quaternary. Professor Le Conte 

 desired to hold his final scientifically expressed opinion in reserve, 

 awaiting further testimony. The interest among scientific men is 

 intense on any subject calculated to show evidence of the an- 

 tiquity of man, especially in Pliocene or Miocene ages. 



Origin and Mode of Formation of Saline Mineral Waters. 

 — M. Dreulefait, in a lecture upon this subject recently delivered 

 before the French Scientific Association, took occasion to dis- 

 credit the usual theories which attribute the formation of the 

 beds of the gypsum, rock-salt, etc., that mineralize such waters, 

 to the action of sulphuric acid from the depths of the globe, or 

 to any other internal agency, and to attribute their origin entirely 

 to causes acting exteriorly to the primitive crust of the earth. 



The rocks forming the first solid envelope must have solidified 

 at a temperature of 2000° to 2500 C, at which chlorine, sulphur 

 and their combinations must have existed completely disassocia- 

 ted in the atmosphere. Chloride of sodium would form at a 

 comparatively high temperature because it can support such a 

 temperature without disassociation of its elements, but chloride 

 of magnesia could not, since it decomposes at 100 C. in the 

 presence of water, have been formed until the temperature of the 

 earth was about 100 C, and the greater part of the water was 

 already condensed. 



Here, then, is the source of the salts found in the earth's crust, 

 in the sea, and in mineral waters. The water, condensed by the 

 lowered temperature, dissolved the soluble salts already deposited, 

 as well as those continuously produced by the action of the 

 acids within it. These salts were principally sulphides and chlor- 

 ides produced by the union of sulphur and chlorine with the 

 metals sodium, lithium, potassium, calcium, and magnesium 

 already deposited in the more ancient crust of the earth. 



Thus the masses of chloric and sulphuric salts which exist in 

 the sedimentary beds of the globe have been formed by the spon- 

 taneous evaporation of isolated portions of the ocean. 



This can be verified by the facts which occur in the evaporation 

 of sea- water for the production of salt. The substances precipita- 

 ted, in the order of their occurence, are : 



1. A feeble deposit of carbonate of lime with traces of strontian, 

 and of sesquioxyde of iron mixed with a little manganese. 



2. Gypsum. This deposit does not occur until the water has 

 by evaporation diminished to one-fifth of its original volume. 



