APPENDIX B. 189 



hours, the bitter water containing the earthy chlorides being thus 

 drained off. Thorough drainage is considered an important point 

 in this mode of manufacture. The balance of the brine or bitter 

 water remaining in the kettle is now bailed out and thrown into the 

 drainage trough. The kettle is then rinsed out with fresh water, 

 and again filled up with brine. 



The difference of the time in which the front and the back ket- 

 tles boil down varies from four hours in the front to twelve hours 

 in the back. The kettle blocks are generally run day and night by 

 four men, two boilers and two firemen, taking tours of twelve 

 hours each. The average product of a good kettle block is seventy- 

 five barrels of salt per day of twenty-four hours. 



EVAPORATION OF BRINE IN PAN BLOCKS. 



Pan blocks are buildings of various dimensions, built to accom- 

 modate the size of the pan, settlers, and salt bins. 



The pans are made of quarter-inch boiler-plate iron. They vary 

 from 90 to 120 feet in length, being divided into sections of 30 or 

 40 feet, are 12 to 1 5 feet wide, and from 10 to 12 inches deep. With 

 some the sides are straight, the salt being raked to the side, lifted 

 out with a shovel, and thrown on the draining boards. In others, 

 the sides are flanged, and the salt is raked directly on to the drain- 

 ing boards. 



Pans of the above size rest on three walls as in kettle blocks, the 

 arches running directly under the pan to the chimney at the end. 

 As the firing of these blocks is done mostly with slabs and light fuel, 

 the first 30 or 40 feet are also protected by patent arches thrown 

 across the flues, thus dividing the heat more generally throughout 

 the block. 



The brine boils very rapidly in these blocks, and as the salt makes 

 fast, it requires much care and attention on the part of the work- 

 men to keep the salt from baking on the bottom of the pan ; this is 

 prevented by raking out the salt almost as fast as it makes. 



Improvements in heating pan blocks have been made of late years 

 in those localities where the price of fuel is a consideration. A 

 pan block of an improved plan for boiling the brine has been erect- 

 ed by Messrs. Ayres & Co., of Port Austin, Huron County. 



The block is 120 feet long, 43 feet wide, outside post 10 feet high, 



