permanent, there was room on the palette for a strictly durable and somewhat transparent pigment like cadmium red, with its many distinctive properties. COCHINEAL LAKES. Lake, a term derived from the _lac_ or _lacca_ of India, is the name of a number of transparent red and other coloured pigments of great beauty, prepared for the most part by precipitating coloured tinctures of dyeing drugs upon aluminous bases. Consequently, the lakes form a numerous class, both with respect to the variety of their appellations, and the substances whence they are produced. Those under notice are known as _Carmine_, _Crimson Lake_, _Scarlet Lake_, _Purple Lake_, _Chinese Lake_, _Florentine Lake_, _Hamburgh Lake_, _Roman Lake_, _Venetian Lake_, &c., and are obtained from the "coccus cacti," an insect found on a species of cactus, from the juice of which it extracts its nourishment. This coccus is a native of Mexico, where two kinds are recognised, under names which signify wild cochineal and fine cochineal. The latter may be considered a cultivated product, its food and wants being carefully attended to, while the former is left in a natural state, and is less valuable. Wild cochineal is distinguished by having a woolly downy coat, which is not the case with the fine cochineal. The females, of which there are from one hundred and fifty to two hundred for each male, are marked by the absence of wings, and constitute the commercial article. They are generally killed by immersion in boiling water, which causes them to swell to twice their natural size, and are then dried and packed for market. The insects shrivel in drying, and assume the form of irregular grains, fluted and concave. The best sorts have a silvery-grey colour, with a purplish reflection, and seem to be dusted with a white powder. This appearance is often given by means of heavy spar, carbonate of lead, Venice talc, &c. A good lens, however, will mostly expose the fraud; or it may be detected by macerating the insect in water, and allowing the loosened pulverised particles to settle. Cochineal is a very rich colouring substance, yielding about half its weight of real colouring matter, which may be easily extracted by boiling in water. Dr. Warren De La Rue, who examined the living animal, states that on piercing the side of the insect a purplish-red fluid exuded, containing the colouring matter in minute granules. This colouring matter he succeeded in obtaining pure, in the form of a purple-brown friable mass, pulverizable to a fine red powder, transparent when viewed by the microscope, and soluble both in water and alcohol in all proportions. At temperatures above 136° it decomposed, and by alkalies its colour was turned to purple. These facts account for the care required in drying cochineal lakes, and for their liability to change of hue when in contact with alkaline substances, as in mural decoration.