The room being at the temperature indicated above, and the bags subjected to a powerful pressure of three hundred tons or more, all the oil is extracted from them, and what is left is perfectly dry, free from any oily matter, and brittle. The oil thus obtained by this last pressing is called _tight pressed_, or _summer oil_. SPERMACETI. What remains after the several pressings, and the removal of all the oil, is called _stearine_, or _spermaceti_. Spermaceti is not confined to the head matter of the whale, as some suppose, nor does the head matter have any thing to do with the brains of the whale, as others have falsely conjectured; but spermaceti is found in the entire oil from the sperm whale. It should be observed, however, that the spermaceti from the body oil of the whale makes harder candles than the spermaceti from the head matter; but the head oil or matter gives a greater proportion of spermaceti, and is more valuable than that from the body oil. Besides, the spermaceti from the head oil is quite different from that of the body oil; the former presents fine, bright, transparent scales, like small particles of isinglass, while the latter is more compact, something like dough. In cooling, one exhibits a sparry, crystalline structure, the other that of clay. Head oil or matter is usually manufactured with the body oil of the whale, and mixed in proportion to one third of the former to two thirds of the latter. SPERMACETI CANDLES. That which remains in the bags after the hydraulic pressure is both dry and brittle. The oil, it is supposed, is wholly extracted, and nothing now remains but the spermaceti. Its color, however, is not white, but interspersed with grayish streaks, bordering on the yellow. The spermaceti is put into large boilers adapted for the purpose, and heated to the temperature of two hundred and ten degrees. It is refined and cleared of all foreign ingredients by the application of alkali. Afterwards water is added, which, with a temperature of two hundred and forty degrees, throws off the alkali in the form of vapor. The liquid which remains is as pure and clear as the crystal water, and ready to be made into the finest spermaceti candles. RIGHT WHALE OIL. The manufacturing of this variety of oil is of recent date, (within twenty-five years.) At first, in preparing it for sale, it was taken in its crude state and "recked off," that is, simply pumped out of the casks, and leaving the sediment behind. This kind of oil then was as cheap as milk is now. BLEACHING OIL. Crude oil is bleached in the first place by putting it into large kettles, applying alkali to it in proportion of one quart of alkali to one barrel of oil, and then heating it to a temperature of one hundred and ten degrees. This process destroys the watery acid in the oil.