80 MANUAL FOR SUGAR GROWERS. 



it will be seen that with a piston at each end of the 

 roller, and with the pressures mentioned, the roller 

 so fitted will be held in its place with a pressure of 

 twenty-four tons, no more and no less, so that no ex- 

 tra strain can be put upon the mill by over-feeding or 

 by a foreign body, such as a stone. Hence the dan- 

 ger of breaking is reduced to a minimum. And what 

 is quite as important, the same pressure of twenty- 

 four tons is exerted upon whatever is between the 

 rollers, whether much or little, so that the same 

 pressure is exerted whether the mill is only partially 

 filled with canes or when fed full. Those who have 

 carefully watched how the crushing varies with the 

 feed in a mill not provided with the hydraulic at- 

 tachment will at once see the value of this flexibility 

 with unvarying pressure. 



Various devices have been arranged to apply 

 springs in the place of the hydraulic press ; some 

 of these are very useful and easily attached to exist- 

 ing mills, and from their simplicity they have much 

 to recommend them. 



It is usual to speak of mills as expressing so much 

 per cent, of the weight of the cane in the form of 

 juice ; it is well at the outset to see that this is an 

 unsatisfactory method of statement, as canes will 

 vary very much in the amount of juice which they 

 contain, so that the same mill might express, say 

 65 per cent, from one lot of canes, and only 60 per 

 cent, from another. A better method would be to 

 ascertain the quantity of moisture left in the me- 

 gass. This should vary less than the quantity of 

 juice expressed. 



