To the foregoing account, R. G. Clements, of Hackney, has been good enough to add remarks substantially as follows. For many years the Newfoundland oil was considered the only sort safe for medicinal use. Norway attempted the extraction, but the imperfect method of its preparation caused it to be neglected in the London market. Of late years, however, great improvements have been made, and now that the Norwegian oil comes in tin-lined casks instead of simply wooden ones, it has quite superseded the Newfoundland brand. An exceedingly fine oil may be prepared on a domestic scale by selecting the quite fresh livers, washing and drying them, puncturing them all over with a pen-knife, and placing them on a dish before a fire. In Norway, three industrial methods are in use :—(1) Exposure to the sun, then boiling is water, and skimming off the oil ; (2) packing into vats provided with three taps, when, after remaining long enough, the oil floats, and is let off by the taps, the uppermost giving the best ; (3) cutting into slices, and exposing to a temperature of 82° (180° F.). All livers which have yielded cold-drawn oil are afterwards exposed to moderate heat for the extraction of straw-coloured oil, and then to stronger heat for brown oil. The property demanding chief attention in oil for medicinal purposes is the presence of free iodine (not added), and all wholesale dealers determine its proportion (by the usual sulphuric acid test) before purchasing the oil.
Crocodile-oil.—The oil of the Indian crocodile contains a larger proportion of solidifiable fat than either neats'-foot or any fish oil. It solidifies at the melting-point of ice, while the others only thicken. In comparison with the softening qualities of other animal oils on leather, it has been found that leather treated with crocodile-oil remained much stiffer than when other animal oils were used. It has been inquired after for leather-dressing in this country, but is not yet a com mercial article here. It is prepared by the Sanif tribe, in the Punjab, who eat crocodile-flesh, and it is said to be abundantly procurable at Agra.
The fat of the alligator (Alligator lucius) is largely utilized. The tail of an alligator of 12 ft. in length, on boiling, furnishes 50-70 pints of excellent oil, which, in Brazil, is used for lighting, and in medicine. The alligators of Central America and the United States might be similarly turned to account.
Dugong-oil.--Of the "dugong," "sea-hog," yungan, or mootla hoora, there are two species, Halicore australis, and H. inclicus, each yielding an oil of great value in medicine and cooking. The latter species is distributed throughout the Indian Ocean, abundantly in the Gulf of Manaar, on the W. coast of Ceylon, between Adam's Bridge and Kalpentyn ; also in the Straits Settlements, and the Eastern Archipelago. The former species is found on the Australian coasts, from Brisbane northwards along the Great Barrier Reef ; in the Gulf of Carpentaria ; in Shark's Bay, W. Australia; and along the N.-W. coast. The pursuit of the animal by Europeans on an industrial scale is almost confined to the Queensland coast, chiefly in Moreton Bay, Wide Bay, Hervey's Bay, Cleve land Bay, and the mouth of the Pioneer River. Only one vessel is sail to be engaged in this fishery at Shark's Bay, W. Australia ; in Ceylon and the Straits, this industry seems to be totally neglected, except by the Malays, who hunt the animal for food.
The animals frequent shallow waters, where the depth does not exceed 2-4 fathoms, and feed on the sea-grasses found in such localities. Their habits are essentially gregarious, and they era sometimes met with in immense herds. The method of capture adopted by the Australian blacks
is to surround the creatures on their feeding-grounds, and drive them landwards, where they kill them by spears. Netting is sometimes successful on a retreating tide ; and harpooning is also practised from boats, which requires great skill and caution. The wariness of the animals places an obstacle in the way' of a development of the industry, as they suddenly desert a feeding-ground and appear elsewhere, where no provision has been made for boiling them down. The assistance of a tender carrying the necessary apparatus will probably have to be brought into requisition.
The size of the Indian animal varies from 6 to 10 ft. ; the Australian sometimes reaches a length of 15 ft. The weight of an average specimen is 4-6 cwt., though they occasionally attain to 10-12 cwt. ; the yield of oil ranges between 6 and 14 gal. usually, but exceptionally amounts to 18 gal. It is obtained from the adipose matter of the cellular substance under the skin, which is boiled down for its extraction. It is free from odour, and has no unpleasant flavour ; when well refined, it is clear and limpid. It loses its fluidity at low temperatures. It is so palatable as to be readily taken by stomachs which reject cod-liver-oil ; in Australia, it is widely used as a substitute for the latter in medicine, though it differs from it in containing no iodine ; it is also employed in lieu of butter, both as an article of diet, and for cooking. Its wholesale value at Perth, W. Australia, is 10s. a gal.
Egg-oil (FR., Haile d'teufs).—There are several methods of preparing an oil from the yolk of eggs. (1) The yolks of new eggs are evaporated in a silver saucepan with constant stirring until the oil exudes on pressing the mass between the fingers ; this is then enclosed in a bag made of ticking, promptly pressed between heated plates, and filtered while hot. This process is preferable to all others when the oil is to be applied to chaps on the skin ; the product is very sweet. (2) The yolks are cooked in a water-bath, with unceasing agitation to hasten the evaporation ; they are kept over the fire till, the oil commencing to separate, they have assumed the appearance of broth ; they are then left to cool ; they are next put into a flask with some ether, and after 24 hours, are poured into a displacer ; the mass is there left to drain, and is exhausted with fresh ether ; the etherized liquors are distilled ; the product is a yellow oil, mixed with viscous matter ; the mass is heated to separate the latter, which isolates itself, and the oil is pressed through fine linen, or filtered hot. The oil thus prepared is sweet, provided that well-rectified ether has been used. As it turns rancid very easily, it is kept in small bottles, tightly corked, stored in cellars. (3) Two parts of fresh yolk of egg are diluted with 5 parts of water ; the liquid is introduced into a vessel with a ground-glass stopper, and 1 part sulphuric ether is added ; the vessel is occasionally well shaken during 7-8 hours. On standing, the ether charged with oil comes to the surface ; it is decanted and distilled ; the residue retains a little ether and animal matter ; it is treated with concentrated boiling alcohol, and filtered ; the alcohol is distilled, and to ensure the removal of every trace of alcohol, ether, and water, the oil is kept in the water-bath ; it is filtered hot ; it is sweet, and of a yellow colour. If the ether solution of the oil does not separate well from the rest of the liquid, a very sligbt heating will effect the purpose.