132 WALKS AND TALKS. 



Caspian, well illustrates, as I have long believed, the method 

 of accumulation of the great salt formations of geological 

 times. In western New York, in certain regions great beds 

 of rock salt may be reached by boring to a certain depth. 

 They lie underneath solid sheets of limestone and thick beds 

 of shale. In the vicinity of Goderich, Ontario, and also in 

 Michigan at sundry localities Marine City, St. Clair, Alpena 

 on the east shore, and Manistee, Muskegon and Ludington 

 on the west shore vast deposits of rock salt are found, at 

 depths from a thousand to two thousand feet. The best of 

 evidence exists that the salt bed is the same on opposite sides 

 of the state, and extends continuously under the state. This 

 is also, the formation which supplies brine for the works at 

 Syracuse. 



Another salt formation occurs in Michigan, occupying a 

 higher geological position than that just mentioned. The 

 first is the Salina formation in the Upper Silurian (see Table, 

 p. 73) ; this is the Michigan Salt Group, in the Lower Car- 

 boniferous. From the last, the wonderful supplies of the 

 Saginaw valley are mostly obtained. From the Salina form- 

 ation the supplies eclipse even those of the upper group. At 

 Marine City, on the St. Clair river, a delightful steamboat 

 ride from Detroit, are works of astonishing magnitude and 

 productiveness. The great salt industry of Cheshire, England, 

 is supported by beds of rock salt sixty to a hundred feet thick, 

 and underlying strata of clay and gypsum, and having indu- 

 rated clays and gypseous beds underneath. Much of the salt 

 is mixed with earthy materials, and hence is redissolved in 

 sea-water, settled and re-evaporated. Other salt deposits of 

 world-wide celebrity occur in Poland, Austria, and Germany. 

 The boring at Stassfurt, Germany, penetrated 1,066 feet of 

 rock salt, and that at Sperenberg, 5,084 feet without reach- 

 ing the bottom. 



It appears, therefore, that the evaporation of sea-water 

 has taken place on a large scale in various ages of the world. 

 In many localities the salt has been again dissolved by fresh 

 water from the surface, and porous formations underlying have 



