120 CHEMICAL MANURES. 



diameter of 290 mm. (say 11| in.), and makes 1000 turns a minute. 

 This latter roll consists of a cast-steel nucleus on which are 

 mounted toothed rings, easy to remove and replace. The machine 

 is surrounded by a protecting cover, with a hopper, into which the 

 material to be ground is fed. The substance passes between the 

 rolls where it is subjected to powerful grinding, produced both by 

 the steel points and the differential speed of the rolls. The machine 

 frees itself automatically from all adherent matter, which is not so 

 with Carr's disintegrator. It is particularly suitable for moist 

 gluey superphosphates. 



Cylindrical Crusher luith tico Bolls fitted luitJi TeetJi. — This 

 machine is used for the same purpose as the foregoing; it is, more- 

 over, used in making compound manures from superphosphate 

 and sulphate of ammonia. The two rolls have a length of 500 

 mm. (say 20 in.) by 500 mm. ; the one turns slowly, the other 

 rapidly. The teeth of one of the rolls pass through the interstices 

 between those of the other, and thus exert a powerful crushing action 

 on the material. It is fitted with a cover forming a hopper, and 

 is combined with an elevator and a shaking sieve. These machines 

 may be grouped in two ways, according to the nature of the super- 

 phosphate. The crusher may be installed at a higher level than 

 the sieve, or on the floor. In the first case, the superphosphate 

 is fed into the receiver of an elevator which discharges it at 

 a higher level into the hopper of the crusher. The superphosphate 

 after passing through the jigger falls on a shaking sieve, the fine 

 material passes through the sieve and falls into the discharge 

 hopper, whilst the core in the sieve returns to the elevator, which 

 brings it back into the crusher, and so on. 



In the second case, where the crusher is fixed on the floor, the 

 matter is charged directly into the crusher, from whence it falls 

 into the cup of the elevator, which spreads it over the sieve higher 

 up. The routine of the operations is absolutely the same as in the 

 first case. But this second method has drawbacks. The cups of 

 the elevator in seizing the material, crush it and transform it into 

 a pasty gluey mass which resists sifting and returns, incessantly, 

 from the sieve into the crusher again, to take the same road and 

 choke up the whole of the apparatus. This drawback disappears 

 if the machines be grouped in the manner indicated in the first 

 instance, in which the superphosphate is elevated before being 

 crushed ; it is then in consistent lumps and stands the action of the 

 cups very well. The sieve itself consists of a shaking table ani- 

 mated by a to and fro motion driven on each side by a pulley and 

 crank. The frame of the sieve is hung in an iron frame, on which 

 the driving pulley is mounted. The sieve is wire woven. It must 

 be kept perfectly clean so that the superphosphate passes through 

 and does not return to the crusher or become gluev. If the sieve 



