106 RURAL MICHIGAN 



600 to 1,000 feet or more, while the Manistee salt 

 is derived from a brine artificially produced through 

 the injection of fresh water from the surface of the 

 ground into the salt formation, in penetrating which 

 it dissolves a quantity of salt which the return flow 

 of water to the surface conveys thither, where it is 

 concentrated and purified. Formerly the evapora- 

 tion of the water from the brine was cheaply per- 

 formed by the use of waste fuel and waste steam 

 from the saw-mills of the locality, so that the timber 

 supply has adversely affected the salt industry of 

 Michigan. Yet recent statistics of salt production 

 show that the industry is on a much larger scale 

 now than ever before. For the past forty years the 

 State has produced more than one-fourth of the 

 national supply of this most necessary article. In 

 addition, by-products, such as bromine, calcium 

 chloride, bleaching and caustic soda, have been de- 

 rived from the salt industry. During the war the 

 production of bromine, especially at Midland, as- 

 sumed great importance. The reserves of salt remain 

 very large, in some places the deposits having a 

 thickness of 500 to 800 feet, at moderate depths. 

 Definite information concerning exact distribution 

 and available quantity of salt in the State is wanting. 

 However, it seems evident that the ancient oceanic 

 beds in which this product is obtained are sufficient 

 for all future requirements. 



In the early period of the gypsum industry, the 

 product was largely utilized as "land-plaster," but 

 with the increasing use of artificial fertilizers, this 



