I called on an individual, in this place, and advised him to subscribe for the Scientific American, but he had doubts about becoming a subscriber. He said, however, if you could tell him how to color a black on cotton and wool, that is, a cotton white welt, and a woolen white warp, without injuring the cloth, he would then believe you understood your business, and would take your paper. I want to be clearly understood: the cloth is white composed of wool and cotton. The person I speak of is a cloth manufacturer. J. T. AiTa, Canada West, Jan. 12th, 1S53. [We are not solicitous about the scrupulous gentleman's patronage, but we can do the very thing he wants. We know how to color a piece of white goods, half cotton and half wool, a good black, and not injure the quality of the goods as much as if it were composed of cotton and wool dyed separately. We can furnish practical receipts for doing this or any other color whatever.