210 KEPOKT OF NATIONAL MUSEUM, 1899. 



York the brine is run in a continuous stream in large pans some 130 

 feet long by 20 feet wide and 18 inches deep. As it evaporates the salt 

 is deposited on the bottom and, by means of long-handled scrapers, 

 is drawn on the sloping sides of the pan. Here it is allowed to drain, 

 and is afterwards taken to the storage bins for packing or grinding.^ 

 Salt thus produced, it should be noticed, is never so coarse as the 

 so-called rock salt, or that which has formed by natural evaporation. 

 In Michigan the brine from the wells is first stored in cisterns, whence 

 it is drawn off into large shallow pans, known technically as "settlers," 

 where it is heated by means of steam pipes to a temperature of 175°, 

 until the point of saturation is reached. It is then drawn into a second 

 series of pans, called "grainers," where it is heated to a temperature 

 of 185°, until crystallization takes place. 



The strength of brines, and therefore the quantity of water that 

 must be evaporated to produce a given quantit}^ of salt, varies greatly 

 in different localities. At Syracuse the brine contains 15.35 per cent 

 of salt; at the Saginaw Valley, 17.91 per cent; at Saltville, Virginia, 

 25. 97 per cent; while Salt Lake contains 11.86 per cent, and the waters 

 of San Francisco Bay but 2.37 cent. The amount of impurities 

 depends on the care exercised in process of manufacture, rapid boil- 

 ing giving less satisfactory results than slower methods. The Syra- 

 cuse salt has been found to contain 98.52 per cent sodium chloride; 

 California Bay salt 98.43 per cent and 99.11 per cent; and Petite 

 Anse 99.88 per cent. The impurities in these cases are nearly alto- 

 gether chlorides and sulphates of lime and magnesia. 



The Cheshire (England) salt beds are worked both by mining as rock 

 salt and by pumping the brine. Formerly both upper and lower beds 

 were mined, but flooding and falling in of the roofs caused the work 

 to be discontinued on the upper beds. That now mined as rock salt 

 comes wholly from the lower bed, and being impure is used mainly for 

 agricultural purposes. 



At Wieliczka the salt is likewise mined from galleries resembling in 

 a general way those of a coal mine. These, according to Brehm,^ 

 begin at a depth of about 95 meters, forming several levels connected 

 by stairways, the lowermost gallery being at a depth of 312 meters, or 

 some 50 meters below sea level. These galleries have a total length of 

 some 680 kilometers. They are connected with one another by means 

 of "onze puits," of which seven are utilized for hoisting purposes. 

 The work goes on continually night and day the year through. The 

 salt is cut out in the form of blocks, leaving huge chambers, the roof 

 being sustained b}^ means of large columns of salt left standing. The 



^For details, see Salt and Gypsum Industries of New York, by Dr. F. J. H. Mer- 

 rill, Bulletin No. 11, New York State Museum, 1893. 

 ''Merveilles De La Nature. La Terre, etc., p. 315. 



