494 ON OUR OIL FLASKS. 



but better for the 12 per cent, of oil to be expressed from them — a 

 clear oil, thick, inodorous, and pale-yellow in colour, used in France 

 for both light and cooking, and in Silesia, by the peasants in the place 

 of butter. And there is the oil of mustard-seed, good for soups and 

 cooking ; and tel oil, or the oil of the Sesamum Orientale, called " oily 

 grain " in South Carolina, and used for soups and puddings like rice, 

 the oil coming in for salads, and, indeed, being often mixed with olive 

 oil : the oil of Ben, already spoken of ; rapeseed oil — the ordinary 

 English rape, which is the best — used for lighting, for the manufacture 

 of soft soaps, in the preparation of leather, and for oiling machinery ; 

 plum-kernel oil, tasting like the oil of sweet almonds, transparent, and 

 of a brown-yellow, soon turning rancid, but much liked in Wurtem- 

 burg for lighting purposes ; and the " butter of cacao," from the 

 nuts of the Theobroma cacao, when crushed in hot water, and had to 

 the extent of 50 per cent. It is yellow, but can be melted white in 

 hot water ; smells and tastes like the cacao nut ; is of the consistency 

 of suet, and keeps long fresh without turning rancid. And, lastly, 

 there is the " butter of nutmegs," prepared by beating the nutmegs to 

 a paste, steaming them, and then pressing them between heated plates. 

 This butter is imported in oblong cakes, covered with leaves and 

 looking like common bricks, of an orange colour, firm consistency, 

 aromatic and fragrant in odour, like the nutmegs themselves — when 

 not wooden. A spurious article is sometimes made of animal fat 

 boiled with powdered nutmegs and flavoured with sassafras ; but it 

 can be easily distinguished by the wary. All these are the non-drying 

 oils, good for food and light, the oils which, as they grow old, get 

 thicker, less combustible, offensive to the taste and rancid, irritating 

 the throat in consequence of the acid that is developed in them. But 

 that acid can be removed by boiling rancid oil in water, with a 

 little magnesia, for a quarter of an hour, or until it no longer reddens 

 the litmus paper. 



Now we come to the drying oils, those which go chiefly to make 

 painters' varnishes, which dry up into a transparent, yellowish, flexible 

 substance, with a skin formed over the surface of the oil, by which all 

 alteration of its condition is stopped. When boiled with litharge, or 

 oxide of lead, they become even more drying, as every painter, fond of 

 experiments, knows ; and if one-eighth of resin is added to the process 

 it greatly improves the look of the painting when dry. First, there is 

 linseed oil, which makes printers' ink when it has been burned and 

 mixed with one-sixth of its weight of lamp-black, which is a final 

 dressing to thin-gummed silks, which varnishes leather and oilcloth, 

 and which, when thoroughly expressed from the seeds, leaves " oil 

 cake" for cattle-feeding and the destruction of pleasant milk and butter. 

 Then there is walnut oil, an even more rapidly drying oil than linseed, 

 used chiefly for paints and varnishes, and, because it gets white by age, 

 for white paints ; and hazel-nut oil ; and poppy oil from the seeds, 



