8Z MODERN HIGH FARMING. 



Each den should be about 12 feet square and 15 to 20 feet high, 

 and must communicate with the shaft or chimney, by means of a 

 good-sized opening, situated near the top, while the air-tight iron 

 doors by which they are entered must slide easily, when pushed 

 backwards or forwards. 



Upon the top of each den is fitted a mixer of cylindrical shape, 

 3 feet in diameter and 4 feet high, made of lead, and encased in a 

 strong wooden frame, with a movable bottom or trap. It must be 

 provided with a large hopper or feeder, and possess a revolving axle 

 fitted with arms or spirals. 



Running into each mixer from the top, under the hopper, is a 

 leaden pipe fitted with a glass stop-cock' communicating with a tank 

 placed directly overhead, and prearranged by mechanical appliances 

 to let out only a calculated quantity of liquid for each batch. This 

 tank communicates in its turn, with the acid chambers from which, 

 when emptied, it is automatically replenished. 



The phosphate is either brought forward from the mill in buckets, 

 by what are known as Jacob's ladders, or wheeled up an inclined 

 plane and emptied into the hoppers of the mixer, where, the acid 

 tap being turned on, the powder and the liquid work into the drum 

 together. 



The agitators are allowed to revolve with swiftness and energy for 

 about five minutes, when, the sliding bottom of the mixer being 

 withdrawn, the whole contents in the form of a thick mud are al- 

 lowed to drop from the drum into the den. 



As the acid in the leaden chambers is frequently found to be de- 

 posited in layers of different strength, care must always be taken to 

 test and thoroughly mix it before allowing it to enter the tank from 

 which the phosphate mixers are supplied, a want of uniformity 

 in this direction being generally, if not always, attended with loss 

 and disappointment. At the end of 24 hours the doors of the dens 

 may be opened, and, if the proportions of the raw material have 

 been properly calculated, the superphosphate will then be sufficiently 

 hard to allow of its removal with the shovel. 



