192 



LOWER PENINSULA. 



thoroughly, twenty-four hours if possible, before going to the bins. 

 It lies in the bins two weeks to complete the drainage, when it is 

 ready for inspection and barrelling for shipment. 



SOLAR EVAPORATION OF BRINE. 



The first preparation for solar evaporation is to have a series of 

 covers or wooden vats. The covers are rectangular in shape, being 

 16 by 18 feet and from 6 to 8 inches deep. They are raised on 

 wooden supports 2 to 3 feet from the ground, and are arranged 

 in sets or strings. Each cover has a movable roof, which can 

 be run on or off to protect or expose the brine, according to the 

 weather. At the end of the string of graining covers, somewhat 

 higher and deeper, are the " strings " of settling covers into which 

 the brine is led from the store reservoirs or cisterns. No lime is 

 used in settling the brine in this process ; for in these deep rooms, 

 the brine absorbs a portion of oxygen from the air, by which means 

 the carbonate of iron, which is dissolved in the recent brine, is con- 

 verted into an insoluble peroxide of iron. In Syracuse, a second 

 series of covers are used to get rid of the gypsum, which separates 

 or is deposited in the form of a crystal. As the quantity of gyp- 

 sum is very small in the Saginaw brines these rooms are nov\; dis- 

 pensed with. 



As soon as there is a show of salt crystals, the first stage of the 

 process is accomplished, and the saturated brine known as salt 

 pickle is ready for the last stage. It is then drawn into the salt 

 room or graining vats, in which the salt soon commences to crystal- 

 lize on the bottom of the covers. 



" One of the conditions required for the production of a good, 

 large-grained solar salt, which is most esteemed in the market, is 

 that the bottom of the covers in the salt room should be as smooth 

 as possible, rough surfaces favoring the deposition of numerous small 

 crystals. It is also necessary to have the salt covers supplied with 

 a sufificient supply of good pickle, so that the salt already deposited 

 may always be covered. An exposure of the salt uncovered to the 

 air favors the formation of new small crystals, and the addition of 

 an unfinished or not sufificiently concentrated pickle produces the 

 same effect. It is also important that the waste or exhausted pickle 

 from which the greater part of the salt has crystallized should be 



