Page:Popular Science Monthly Volume 45.djvu/119

Rh as seventeen dollars a ton, but there is no profit to the millers if they pay much over twelve dollars. A sharp competition among them led to the forming of an association of the mills in 1878, which was the forerunner of the American Cotton-seed Oil Trust. The Southern States are now divided into districts, each one supplying certain mills, and keeping a uniform price for the seed.

The bulk of the supply is obtained from plantations immediately upon the Southern rivers, because the seed can be transported at little cost. The mills are also located upon the rivers. Once landed at the mills, the seed is conveyed in an elevator to a screen, or cylindrical sifter, where it is shaken until it is free from dust and sand. Then it is blown against another screen to remove stones, iron, and other foreign substances that might injure the rollers. A second elevator carries the seed to the loft, where another sifter separates the seed proper from the bolls or outside hulls of the cotton bloom. No matter how close the picking may have been, the bolls still have cotton sticking to them, and they are dropped into a gin to remove the lint. This is known as "crapo cotton," the only variety of linter produced in the mills. The seed having fallen through the screen, is carried along another screen or gutter directly over the gins. They drop through holes in the screen upon the gins; but when the box above the gin is full the hole is closed automatically, and the screen carries the seed forward to the next box, thus keeping all the boxes full. The gins differ from cotton gins in having one hundred saws instead of sixty. The saws are but half an inch apart and the teeth are very firmly set. The problem of wholly removing the lint, save by chemical process, has not yet been solved.

Once thoroughly separated from all foreign substances—dust, bolls, and cotton—the seed is conveyed to the roller, a revolving cylinder containing twenty-four knives and four back knives, which cuts the hulls from the kernels. This process was formerly carried on by grindstones. The hulls go upstairs, where they are again treated to find such kernels as may still be clinging to them, after which they are sold or used as fuel in the furnace of the mill. Only half of them are needed for this purpose, the other half being sold as food for cattle. The ashes of the hulls make an excellent lye for soap or for the refining of the oil. The kernels are conveyed to rollers, where they are crushed very fine. They are thence removed to the heaters, being agitated all the time so as to give an equal exposure and allow the oil to be more readily extracted. The kernels are then placed in woolen bags packed between horse-hair mats, backed with leather, and having a fluted surface inside to allow the oil to escape more freely. The hydraulic pressure, furnished by the oil itself instead