HOW TO INCREASE THE YIELD OF JUICE. 129 
yield, the most perfect system should be strictly observed. 
The mill should not only be regulated to a uniform speed, 
but should be of sufficient power to work off the entire 
crop without requiring the speed to exceed the rate which 
will permit the juice to flow off readily before the begassa 
is liberated from the mill, so that this begassa may not in 
expanding act as a sponge, to absorb a large proportion of 
the expressed juice. The importance of grinding at a low 
speed is rendered evident by the following mean results of 
numerous experiments made by the Marquis de St. Croix, 
a very intelligent planter of the Island of Martinique, and 
which I extract from a work* he has written on the manu- 
facture of sugar. 
““With the same mill, and its rollers set in the same way, 
the juice obtained constituted 45 per cent. of the weight of 
the canes ground when the rollers made six revolutions in 
a minute, and 70 per cent. when the velocity was only two 
and a half revolutions per minute; a diiference of 25 per 
cent. 
“As the surface developed is for an equal aumber of rev- 
olutions proportional to the diameters of the rollers, M. 
de St. Croix asserts that a good result will be obtained by 
rollers which develop a surface of four or five yards in 
length per minute, so that a roller of two feet diameter 
should make from two to two and a half revolutions per 
minute. 
“And if it be objected that this velocity is insufficient 
to express the requisite amount of juice in a given time, 
then the length of the rollers should be increased, and, if 
necessary, also the power of the engine. It is the quantity 
of juice required per hour, under circumstances the most 
favorable for perfect extraction thereof, which should deter- 
mine the power of the engine to be employed.” 
* Fabrication Actuelle de Sucre aux Colonies. Paris, 1843. 
