The horny or flinty portions of corn, when viewed in their sections under a good microscope, will be found to consist of a great number of six-sided cells, filled with a fixed oil, which has been successfully used for the purposes of illumination. On this oil depends the popping qualities of corn ; for when the kernels are heated to a temperature sufficiently high to decompose the oil, a sudden explosion takes place, and every cell is ruptured by the expansion of gaseous matter, arising from the decomposition of the oil and the formation of carburetted hydrogen gas, such as is sometimes used in lighting large cities, the grain being completely evolved and folded back, or turned inside out. This property is remarkably strong in the pop corn, and is common in a greater or less degree in all corn abounding in oil ; but those kinds destitute of a horny cover will not pop under any circumstances. After the decomposition or extraction of this oil, corn is more readily digested by man, though it is less fattening to animals.