For each kilogram of tissue which has been previously scoured and bleached, there are provided 200 grammes of cream of tartar and 250 grammes of alum. These are dissolved in the bath of water of the vat, the temperature is raised to boiling heat, and the tissue is immersed in the bath f of an hour while it is worked over through the opening for manipulation. The pieces are then taken from the bath, to which is added a solution of the carmine in water containing a quantity of coloring matter proportionate to the intensity of the blue sought for. The solution ought to be prepared with care and passed through a silk sieve, so that the small insoluble grains which might have been left through bad fabrication may be left on the sieve. After the pieces have been manipulated in the colored bath, so as to exhaust the color and obtain the required blue, they should be rapidly washed in running water and dryed in the shade. Silk stuffs are dyed in the same way; but the alum should be previously applied cold by means of a saturated solution of alum, in which the stuffs should be immersed for an hour. COLORS NOT FAST. In regard to all the combinations of indigo with sulphuric acid, including the carmines, it must be observed that their application does not constitute true indigo dyeing: the colors are not fast. It is not pure indigotine which is fastened on the tissues as in the vat dyeing, but another compound of indigo with the sulphur. Berzelius observes that “the color of soluble indigo is fully as alterable and fugacious as that of the colors extracted by the decoction of vegetable materials. By a long exposure to the sun the indigo blue is destroyed: it becomes green during evaporation, and changes its nature.” The carmines as well as the sulphur acids are easily decolorized by reducing agents, such as hydrogen and sulphuretted hydrogen, although they gradually assume their original color when exposed to the atmosphere. We are informed by some of the older dealers that imported cloths and merino stuffs known as “Saxony” were formerly largely sold in our shops, but that, notwithstanding their attractiveness to purchasers, they were objectionable on account of the instability of their color. APPLICATION OF INDIGO IN PRINTING STUFFS. Our notes would be incomplete without some reference to the uses of indigo in printing fabrics. In pursuing this branch, we are embarrassed on the one hand by the consideration that the subject is too technical for the general reader, and on the other by the consciousness that it would be presumption in us to attempt to instruct those skilled in the art. It may not, however, be without benefit in producing a higher appreciation of science for the general reader to observe how science comes in play, even in the printing of a single color; while to the skilled reader our notes may possibly be of value as a vehicle for conveying some receipts taken from works not easily accessible.