_Rubric Lakes_, or _Field's Lakes_, are derived from the root of "rubia tinctorum," a plant largely grown in France and Holland, whence the bulk of that used in England is obtained. The French madders are in a state of very fine powder, containing one half their weight of gum, sugar, salts, and other soluble substances, which water speedily dissolves. Madder roots in the unground state are imported from the Levant, and called Turkey roots. Good qualities of Turkey madder yield near sixty per cent of extractive matters, a term that includes everything removable by water and dilute alkalis: the woody fibre is therefore about forty per cent. This is presuming the root to be genuine, for madder is often adulterated with brickdust, red ochre, red sand, clay, mahogany sawdust, logwood, sandal and japan-wood, and bran. Unlike cochineal, madder possesses several colouring matters; the question of which, despite the learned researches of Dr. Schunck and others, is far from settled yet. The following remarks embody our own experience of the root, simply as a pigment-producing product:-- Madder contains five colouring matters--yellow, red, orange, purple, and brown. Of these, the first colour is soluble in cold water. By washing the powdered root quickly with it by decantation, the yellow and brown are extracted in the form of an opaque liquid. If this be decanted and allowed to stand, the brown deposits, leaving a clear buffish-yellow supernatant liquor. In the root from which the extract was poured, the remaining three colours are left. On adding a strong boiling solution of alum, these are dissolved, yielding a fine red liquid. From this there can be thrown down, by the agency of different chemicals, a red, an orange, or a purple precipitate. Or, supposing the whole of the colouring matter to be deposited as a red lake, it is possible to convert this--also by the agency of different chemicals--either into orange or purple. Hence, for all practical purposes, madder contains but three colouring matters: a yellow, soluble in cold water; a brown, not soluble in, but capable of being extracted by cold water; and a red, soluble in boiling alum, and furnishing at will a purple or an orange.