Colza-oil is that which is chiefly in use in families for the moderator-lamp. It is the oil of the Brassica Arvensis, which is grown in France and Belgium. It is pressed from the seed, and purified and whitened by sulphuric acid. It is often adulterated by mixture with the oil of the Brassica raptis - i.e., clarified rape-oil. When pure it does not smoke, and has no unpleasant smell. Both the light and cleanliness of the lamp depend greatly on the purity of this oil.

Petroleum and Paraffin lamps cannot be recommended. They always smell unpleasantly, and the latter are attended with some risk. Insurance offices expect a higher rate of premium where paraffin is used. If, however, it is made use of, it should be tested out of doors before it is put into the lamp, by pouring a very little into a flowerpot-saucer and applying a light to it. If it does not explode it may be used.

Sand, Glass, and Emery Papers.

Sand paper and glass paper are made of sand or powdered glass glued on to cartridge-paper. Price 1/2d. per sheet.

Emery is a stone ground in mills and suspended in water. The finer sort is found in the water drawn off first; the coarser follows. It is glued on paper in the same way as sand and glass, or can be used in the powder. It should be bought at the best shops, as there is great difference in it. Good emery paper will last for two or three cleanings; the bad rubs off the first time. Price 3/4d. a sheet.