The colored writing inks, of which "red" is the more important, are in great number and with hardly an exception at the present time, manufactured by adding water and water-glass to a soluble aniline red color. Cochineal which was used for red ink formerly is now almost obsolete. Nigrosine, one of the best known of them, is much used as a cheap "black" ink, but as it is blue black and never becomes black, it really belongs to the family of "colored" writing inks. They possess an undeserved popularity for they flow freely from the pen which they do not corrode, nor do they thicken or spoil in the inkwell; they are however very "fugitive" in character and should not be employed for record, legal, monetary or other documentary purposes. The indigo and prussian blue inks are well known, the former under certain conditions a very permanent ink, the latter soon disintegrating. Copying inks are of two kinds, one dependent on the addition of glycerine, sugar, glucose or like compounds to the black writing inks or chemical writing fluids heretofore mentioned, which are thereby kept in a moist offsetting condition; the other due to the solubility of the pigmentary color with water, such as the aniline inks which are given more body than those for ordinary purposes--and the logwoods in which the pigment is developed and given copying qualities by chemicals, and hence becomes responsive to the application of a sheet of paper dampened with water. Copying ink should never be used for "record" purposes as it is affected by changes of the temperature. India ink, sometimes called China ink, or as formerly known by the ancients and in classical and later times "Indian ink," is now used more for drawing and engrossing than it is for commercial purposes. It belongs to the "carbon" class and in some form was the first one used in the very earliest times. In China it is applied with a brush or pith of some reed to the "rice" paper also there manufactured. It is easily washed away unless bichromate of ammonium or potassium in minute quantities be added to it, and then if the paper on which it appears be exposed for a short time to the action of the actinic rays of sunlight, this gummy compound will be rendered insoluble and cannot be removed with any fluid, chemical or otherwise. It possesses also great advantages in drawing, since it acts as a paint, and will give any degree of blackness according to the quantity of water mixed with it.