236 SKETCHES OF CREATION. 



cient channel, and, plunging headlong down the precipice, 

 began again the practice of that stupendous system of en- 

 gineering which it had already so well learned to wield. 



As the continent slowly rose from the sea, innumerable 

 depressions in the newly-exposed surface were left filled 

 with the brine. Thus the basins of the great lakes of 

 North America were first filled. But an outlet existed 

 from these lakes to the ocean. When the accession of 

 water from the clouds produced an overflow, the drainage 

 was always saliferous. Thus these lakes have always been 

 giving out brine and receiving only pure water. As a con- 

 sequence, their original brine has been continually diluted, 

 until, in our age, its salinity is no longer perceptible to the 

 taste. Nevertheless, chemistry has a tongue that still de- 

 tects the salty savor. 



Not a few of the ancient depressions found no outlet. 

 The ocean's brine, imprisoned within impassable barriers, 

 has there remained, and "salt lakes" are the result. In 

 many instances the brine of these lakes has even been con- 

 centrated in the progress of time. The evaporation of pure 

 water from their surfaces has exceeded the precipitation 

 from the clouds within the limits of their hydrographical 

 basins. This is probably the case with most existing salt 

 lakes, of which the Caspian Sea is our largest example. 

 Some of these salt lakes, in the progress of evaporation, 

 have greatly shrunken in geographical extent. Their aban- 

 doned territory is often saturated with saline constituents 

 rejected by the overburdened water. Some of the salt and 

 alkali plains of our Western Territories have had an origin 

 of this kind. It can hardly be doubted, however, that 

 the great salt-plantations of Nevada result from dried-up 

 streams which take their origin in salt-bearing formations 

 built into the frame- work of the sierras. 



We have now arrived at a point where we can read the 



