22 BOARD OF AGRICULTURE. 



pans, or wooden vats ; the more rapid the process of manufacture, 

 the smaller are the crystals resulting from one and the same 

 brine. In Europe, almost all the boiled salt is manufactured in 

 a system of large pans of from four hundred to one thousand two 

 hundred square-feet capacity ; in most of our own salt-boiling 

 establishments are used hemispherical cast-iron kettles of from 

 one hundred and twenty to one hundred and forty gallons 

 capacity. The kettle system is exclusively used at the Onon- 

 daga Works, N. y. ; in the Saginaw Valley, in Michigan, are 

 employed, besides the kettles, large wooden vats heated by 

 steam ; in Ohio and South-western Virginia is, for weak brines, 

 the so-called furnace-system in operation, which may be con- 

 sidered a combination of direct heat and steam heat, for evap- 

 oration. The steam heat being applied at the more advanced 

 stages of evaporation produces a larger-sized salt. The best 

 qualities of Virginia brines, for instance, at Saltville, in North- 

 western Virginia, are very successfully worked in cast-iron 

 kettles. Inferior brines, particularly those which contain a 

 larger proportion of the chlorides of calcium and magnesium, 

 as a general rule, are best worked by a slow process of evapora- 

 tion, for the salt crystals are in that case more perfectly devel- 

 oped, and the inferior mother liquors consequently best ex- 

 cluded. 



The process of salt-making is quite obviously an operation for 

 the separation and thus purification of the chloride of sodium 

 (salt) from its accompanying foreign admixtures ; the general 

 rules, which apply to the proper management of a successful crys- 

 tallization, find their application here. Brines which contain a 

 considerable percentage of the sulphate of lime, or of soda, or 

 of magnesia, or several of them, produce always smaller crys- 

 tals than those which contain less or none. The boiled salt of 

 the Onondaga brines is, on that account, always smaller and more 

 compact than that manufactured from the brines of Michigan, 

 Ohio and Western Virginia. The European system of manu- 

 facturing common fine salt in a system of large iron pans, — a 

 fore-heater and a grainer, — our own modes of making fine salt in 

 wooden vats by means of steam, the furnace system of Ohio, and 

 the Chapin system of Saginaw differ in one essential feature from 

 the kettle system ; they aim at the removal of certain impurities 

 in a separate vessel and the making of the salt in another one, 



