OILS, DIANUFACTURE OF. The manufacture of animal oils, such as that of the whale, is simple. The blubber, or fat from which the oil is procured, is usually cut into small pieces and packed in casks soon after it is taken from the whale ; it is then brought home in a ludf-putrid state, and is emptied into a large wooden vessel or receiver, capable of holding several tons. From this receiver the decomposing fat is conducted, after settling for a few hours, into a copper boiler, in which the separation of the fluid from the solid portions of the blubber is completed by the application of heat. From the boiler the oil flows through a kind of filter of brushwood, which detains the grosser impurities, into coolers, from which, when quite cold, it may be drawn off into casks. Various chemical processes are employed for purifying whale oil and diminishing its unpleasant smell. The quantity of oil obtained is about four-fifths that of the blubber used. In tho South-Sea fishery it is found advisable to boil the blubber on board the whaling vessels, and to bring home the oil in the liquid state in casks. In this process, as commonly performed, the oil is very imper fectly extracted from the blubber, and the scraps, or solid portions which remain, are used as fuel under the try-pots, or boilers ; by which arrangement the oil that remains in them is not only destroyed, but the substance becomes, from its great inflammability, a source of serious danger. To obviate the evils some ships are provide' with powerful screw-presses for squeezing out whatever oil may remain after the process of boiling the blubber, and thus materially in creasing the produce. Hebert, in the ' Engineer's and Mechanic's Encyclopaedia; gives an engraving and description of such a press; in which the blubberscraps, while yet warm, arc put into a hollow cylinder, and compressed by a piston brought down upon them with great force. The oil escapes through holes in the bottom of the cylinder, between which and the blubber is laid a mattress of wicker work, to prevent the blubber from choking up the holes. This press
is the invention of Mr. John Blythe, of Limehouso.
Olive oil differs from most vegetable expressed oils in being extracted from the soft fleshy pericarp ; whereas such oils are usually procured from the seeds only. The manufacture is simple, and is usually con ducted with very rude machinery. In the neighbourhood of Aix, in l'rovence, the first and finest oil is obtained by crushing the olives in a kind of mill, in which the crushing-stones are so mounted as not to break the atomics of the fruit, but simply to crush the pulp. The mass thus bruised Is put into robes, or bags made of bulrush-matting, or of coarse canvas, which are piled or laid upon one another to the number of about a score, and exposed to gradual compression in a screw-press ; the oil which flows from the cabas, which is the pure virgin oil, is conducted by channels into casks or stone cisterns partly filled with water, ou the surface of which it floats so that it maybe readily col lected by skimming. When the oil ceases to flow, the mass of pulp is taken out of the bags, mixed with boiling water, and treated as before, but with an increase of pressure. The second quality of oil thus procured is quite fit for table use when fresh, but is apt to become rancid by keeping. After skimming off the oil which accumulates on the surface, the subjacent water still retains a good deal of oil, by the intervention of the mucilage ; but after long repose in a large cistern the oil and water separate, and the water may be drawn off from below. This oil, however, is of very inferior quality, and can only be used for factory purposes. A still coarser kind of oil is finally procured by crushing the mare, or solid residue, in a mill, so as to break the stones, boiling it with water, and re-pressing it. All the oil must be fined by keeping in clean tuns, in an apartment heated to at least 60° Fahr., for twenty days ; after which it is run off into strong casks, cooled in a cellar, and then sent into the market.