« 4 • 



MANUFACTUEE OF SUPEEPHOSPHATE. 



]C1 



undergoes very energetic grinding ; when it is reduced to the desired 

 fineness it passes through 

 the bars of the grate as a 

 pulverulent product con- 

 taining more or less core. 

 For a width of | of an 

 inch the yield per hour is 

 about 2 tons of degreased 

 bones. 1 (See pp. 173 et 

 seq.) 



Elevatcrs. — Cup ele- 

 vators are generally used. 

 Gall'swTOught-iron chain 

 and Ewart's chain de- 

 serve notice. These con- 

 sist of small elements 

 moving one within the 

 other after the style of 

 a hinge. Leather belts 

 and rubber belts are only 

 used exceptionally. The 

 cups are of wrought-iron 

 and furnished in the front 

 w^th a steel armature ; 

 they are screwed on the 

 elevator. Their dimen- 

 sions vary with the size 

 of the factory. Cup 

 chains are generally fitted 

 with a tight cover, enclos- 

 ing the whole machine, 

 and thus preventing the 

 disengagement of dust in 

 the factory. This cover 

 comprises a cast-iron feed 

 vessel with the top part 

 of wrought-iron, and two 

 square wrought-iron pipes 

 carrying at their upperex- 

 tremity a hood or coping 

 of wrought-iron fitted with 

 a discharge pipe ; wooden 

 feed vessels and covers 



may be made on the spot. 



Fig. 18. — Cup-chain Elevator. 



^ This output abnormally high even for degreased bones through such a fine 

 sieve, seems quite out of the question for raw bones. Bone grinding to such fine- 

 ness is a tedious process. These machines, moreover, are like " short distance 

 sprinters " — they soon fall out of gear, the belt comes off or breaks, the 

 machine is blocked or the blades are smashed. — Tr. 



