122 PROCESS OF MANUFACTURE. 
waste of time as well as of materials, and is very injurious 
to the grain of the sugar. In all cases when the choice 
must be between drainage by pressure and the reduction 
of the sugar to the condition of syrup, the former alterna- 
tive should generally be accepted; but I would recommend 
that the sugar after the first pressure be washed but once, 
with a small quantity of cold water, and then pressed a 
second time. If it be then melted and recrystallized in the 
proper manner, a fine quality of sugar, of large, sharp 
grain, will be the result. This sugar will drain well either 
in moulds or the crystallizing boxes. This plan is not 
wasteful, for the drippings form a good quality of syrup. 
There are other means of drainage that might be resorted 
to more or less successfully, such as driving the molasses 
through the crystallized mass by atmospheric pressure to- 
ward a vacuum formed by the action of an air pump, as is 
the practice in some refineries. But of all artificial methods 
of drainage, by far the most rapid and thorough is that 
which is accomplished by the use of the centrifugal mill. 
This simple machine has been adopted very generally of 
late years in sugar manufacture, both in tropical countries, 
and in France and Germany. It is one of a number of im- 
provements by means of which, in Cuba and Java, the 
sugar cane is now made to yield almost twice the quantity 
of sugar which was obtained from an equal weight of the 
canes half a century ago. It seems to be admirably adap- 
ted to meet the wants of the sugar manufacturer at the 
North. Although the method by natural drainage is not 
likely to be supplanted by any other, when it is conducted 
under favorable circumstances—that is, when a uniform and 
sufficiently high temperature can be maintained in the drain- 
ing-room, and a good crystallization has been secured—it 
is extremely convenient as well as economical for the oper- 
ator to have at hand a machine by which obstacles to nat- 
