WOOD-OIL OR TUNG-OIL.--This fatty oil is a product of the so-called “oil tree” of China, Cochin China, and Japan (_Aleurites cordata_ [_Elæococca vernicia_, _Dryandra cordata_]), and must not be confounded with the Malayan article, which is an oleo-resin. The fruit capsules of the _t’ung_ are filled with rich oil-yielding kernels, from which 35 per cent. by weight of oil may be obtained by simple pressure in the cold. The sp. gr. of the oil is 0·9362 at 59° F. It possesses several remarkable properties: heated to 212°-392° F. out of contact with the air, it retains its original limpidity after cooling, but in contact with the air it solidifies almost instantaneously, melting again at 93° F, and exhibiting the same elementary composition; the cold expressed oil rapidly solidifies by light in the absence of air; and its drying qualities exceed those of any other known oil. It is devoid of colour, odour, and flavour. The oil is produced in immense quantities in China; in the provinces of Ichang and Szechuen, it is one of the principal articles of native manufacture. In China the oil is universally employed for caulking and painting junks and boats, and for varnishing and preserving woodwork of all kinds. The oil is unknown to European commerce, but an attempt to naturalise the tree in Algeria has been projected. Its industrial value has been too long neglected. EXTRACTION OF SEED-OILS.--The old-fashioned crude apparatus for extracting oil from seeds, which answered the purposes of our forefathers, has had to give way to modern improved machinery, such as that manufactured by Rose, Downs & Thompson, of Hull, and shown in the subjoined illustrations. [Illustration: Fig. 33.--SEED-OIL MILL.] The arrangement of the mill is shown in plan in Fig. 33 and in elevation in Fig. 34. The seed or other material passes through the following course:--It runs from an upper floor through the roll frame A, by which it is crushed three or four times; it is then taken by the elevators B to the kettle C, where it is heated and damped. From beneath the kettle, it is drawn, in quantities sufficient to make a cake, by a box which conveys it to the moulding machine E. Here it undergoes preliminary compression, the objects of which are (1) to increase the number of cakes which may be inserted in the presses at one time, enabling 18 12-lb. cakes to be made where 4 8-lb. cakes were formerly made, and (2) to ensure uniform size and weight, and uniform density or consistence throughout. [Illustration: Fig. 34.--SEED-OIL MILL.]