The oil previously alluded to as being obtained from the kernels of the seeds after removal of the tallow is extracted in the following manner :—The seeds are ground between mill-stones, which are heated to prevent clogging by the tallow still adhering. The mass is then winnowed, and the clean kernels are steamed, and mashed in a cumbrous edge-runner mill. The meal is steamed in tubs, made into cakes, and pressed, the whole course of operations being performed twice. The yield is about 30 per cent. of the cleaned kernels. The oil is used for varnishing umbrellas, anointing the hair, and medicinally ; it burns well in lamps, but is inferior to some other oils in use for that purpose. The seed-husks and tallow-refuse are employed as fuel ; the seed-cake forms a good manure, especially for tobacco.
(b) Malayan.—In Borneo, Java, and Sumatra, are several species of Hopea, producing nuts, which, when compreseed, yield fatty oils, extensively used under the names of " vegetable tallow" and "vegetable wax." Three species of this genus are common in Sarawak ; the one most valued for producing oil is a fine tree growing on the banks of the Sarawak river to a height of 40 ft.; its fruits are produced in the greatest profusion about December-January, and are as large as walnuts. These nuts are collected by the natives, and yield a very large proportion of oil, which, on being allowed to cool, takes the consistence of sperm, and in appearance very much resembles that substance. The natives at present only value this as a cooking oil ; but when the demand for it in Europe becomes better known to them, they will doubtless increase their manufacture of it. In England, it has proved to be an excellent lubricator for steam machinery, far surpassing even olive oil ; and it has been used in Manila in the manufacture of candles, and found to answer admirably. As it becomes more common, it will doubtless be applied to many other purposes. From the quick ness of its growth, and the great profusion with which it bears its fruit, it will, should the demand for it continue, become a profitable object for cultivation, by which the quality and quantity would most likely be improved and increased. It is also found in Java and Sumatra. In Borneo, some 10 species are recognized by the natives, their nuts varying much in size. The kernels are covered with a bard shell, to separate which it is necessary to immerse them in water for 3-4 days. After the separation, they are exposed to the eun for about the same number of days, until the oil begins to exude ; they are then pounded in a mortar, and hoiled in water for some time ; after which, the oil is expressed while hot. This oil has nearly the consistence, and something of the appearance,
of tallow, but is generally yellower. It is found in the markets in rolls 14-3 in. in diameter. It is used in the interior almost exclusively for lighting and culinary purposes. A vegetable tallow is also afforded by the seeds of Tetranthera laurifolia, widely dispersed over Tropical] Asia, aud the E. Archipelago, as far south as New Guinea. In Java and Cochin China, it is commonly used for making candles, notwithstanding its disagreeable odour. The exports of vegetable tallow from the state of Sarawak in 1879 were valued at 7305 dollars (of 4s. 2d.).
Both Chinese and Malayan kinds of vegetable tallow, like shea-butter, are glycerides, and con tain about 95 per cent, of saponifiable matter, which has much less oleine in it than animal tallow.
(c) African.—A so-called vegetable tallow or butter is obtained in Sierra Leone from Pentadesma butyracea; the tree yields from its several parts, especially the fruit when cut, a yellow fatty juice. The fat of a species of Pentadesma, under the name of kanya, is used for culinary purposes is the neighbourbood of Zanzibar, and is said to remain sweet for a long time.
Walnut-oil (Fe., Huile de Noix).—The albuminous kernel of the walnut (see Nuts, p. 1360) affords some 50 per cent. of oil. It is said that it furnishes one-third of all the oil made in France ; it is extensively prepared in the central and southern departments, notably Charente, Charente Inferieure, and Dordogne, where it is commonly met with in barrels of 50 kilo. In both Spain and Italy, outside the olive-region, walnut-oil is largely expressed. It is of considerable importance in the hill districts of India, but is seldom seen iu the plains. Cashmere and Circassia also include it among their industrial products.
The oil should not be extracted from the nuts until 2-3 months after they have been gathered. This delay is absolutely necessary to secure an abundant yield, as the fresh kernel contains only a sort of emulsive milk, aud the oil continues to form after the harvest has taken place ; if too long a period elapse, the oil will be less sweet, and perhaps even rancid. The kernels are carefully freed from shell and skin, and crushed into a paste, which is put into bags, and submitted to a press ; the first oil which escapes is termed "virgin," and is reserved for feeding purposes. The cake is then rubbed down in boiling water, and pressed anew ; the second oil, called "fire-drawn," is applied to industrial uses. The exhausted cake forma good cattle-food.