PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 451 



■which the cane passes; the first of these spaces is about five-eighths of an 

 inch in thickness, while the second is not thicker than a case-knife. In the 

 larg'e mills the rollers are some six feet in length; the longest that I ever 

 saw wore seven feet six inches. A trough, of a width equal to the length 

 of the rollers, extends back from the mill 100 feet, and into this the cane is 

 thrown to the depth of about eight inches by a gang of negroes standing 

 along on each side. The mill takes out from 15 to 85 per cent of the weight 

 of the cane; the juice running off in quite a brook. The woody matter 

 remaining, the begasse, as it is called, is used after being dried in the sun, 

 as fuel for driving the engine. Some of the sugar mills in Cuba have cost 

 $250,000 each. 



THE BOILING. 



Four boilers are used for evaporating the water from sugar. The first 

 holds 600 gallons, the second 400, and the other two 300 gallons each. As 

 the juice is boiled down, a scum rises on the surface, and is skimmed oif. 

 After the liquor reaches a certain density, as measured by a saccharometer, 

 it is dipped out by ladles into the next boiler, where the process is repeated. 

 In the last boiler it is concentrated to the granulating point. 



THE GRANULATING.^ 



When properly condensed the syrup is poured into conical moulds simi- 

 lar to those used in the refineries of this city, only larger. The molasses 

 drains ou<t at the bottom of the mould, leaving the sugar. It is customary 

 to cover the sugar in the moulds with a layer of moist clay, the weight of 

 which aids in forcing out the molasses and purifying the sugar. 



THE PRODUCT. 



Many estates in Cuba now turn out an article of really refined sugar, the 

 mills being supplied with everything to be found in a New York refinery. 



MAKING SUGAR FI#M MOLASSES. 



Dr. Rich. — I am told that a good deal of sugar is now made in this city 

 from molasses. The molasses yields some 30 or 40 per cent of a second 

 quality sugar, leaving a very inferior quality of molasses. 



CENTRIFUGAL EXTRACTERS. 



Dr. Rowell. — In some of the refineries the molasses is separated from the 

 sugar by centrifugal force. A drum, the periphery of which is formed of 

 fine wire cloth, is caused to rotate with great velocity, and on placing the 

 concentrated syrup in this drum, the molasses is thrown out through the 

 meshes of the cloth, while the sugar is retained within the drum. 



Mr. Brewster. — These machines are in general use, both in our city re- 

 fineries and on the Cuba plantations. It is the common method of remov- 

 ing the molasses. Some of the large mills have a dozen centrifugals. I 

 have seen one that would hold 600 pounds of sugar, and the molasses was 

 completely removed from this mass in fifteen minutes. 



Sugar from Grain. 



Mr. Bartlett. — Considerable excitement has been raised in relation to the 

 new process for obtaining a large quantity of sugar from corn. It is well 

 known that starch, when treated with sulphuric acid, yields grape sugar. 



