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Henry Wisner to B. Towne



Philadelphia, December 21, 1775.

Having for many months been sensibly affected with the great disadvantage the Colonies labour under for want of ammunition, I thought it my duty to apply myself to the attainment of those necessary arts of making saltpetre and gunpowder: and having far exceeded my expectations in both manufactures, I think myself still further obliged to communicate the so much needed knowledge to my country at large. My first trial was on saltpetre, two pounds of which my son has extracted from about six bushels of stable dirt, perfectly fit for making gunpowder. This was done by the method of Doctor Young and Mr˙ Rubsaman, lately published by the former, for which, and many other useful informations, I take this opportunity to return those gentlemen my publick thanks.

I have lately erected a powder-mill in the south end of Ulster County, in the Colony of New-York, at which I have made as good powder as I ever have seen, and will bear the inspection of good judges, in the following manner: Gunpowder is composed of nothing more than the four plain simple articles, saltpetre, brimstone, charcoal, and water. The three first of which are to be made as fine as possible, so as to be sifted through a gauze sieve, or fine bolt, as fine as for common flour. But it being difficult to make the saltpetre all fine, those parts that will not be easily got through the sieve, must be dissolved in soil warm, water, then let the sulphur, saltpetre, and charcoal, be each separately weighed. Take of the saltpetre an hundred weight, of the sulphur fifteen pounds, and charcoal eighteen pounds, and in that proportion for any greater or smaller quantity. This being done, mix them all well together in some large vessel, such as a potash or any other kettle, and when well mixed, moisten the whole with the aforesaid nitrous water till it is as moist as dough for making bread. Then put an equal quantity in each mortar, and pound it well for at least twenty hours; and if the mill runs slowly, let it run twenty-four hours; and as the paste, by pounding, will naturally grow dry, it must be kept moist by putting in a little of said water, and when pounded sufficiently take it out of the mortar, and put it in some tub or any other proper vessel. As to the graining, it must be done in the following manner, viz: have a box made about five feet square, the sides eighteen inches deep, the bottom tight, and top entirely open; fix across the box two rods or laths near the middle, about four inches below the top, and about ten inches apart, then have six sieves made of wooden splits in the same manner as a wheat riddle, but much finer, the coarsest should be about as fine as a cockle sieve, or a little finer, and so each sieve to increase in fineness till the last is as fine as possible; I believe it were best to make the two coarsest of wire. Then take about a quart of the paste, put it into the coarsest sieve, set the sieves on the two rods that are fixed across the box, then work the sieve with a circular motion, which will press the paste through the sieve in large and unshapely grains; and when a considerable quantity is passed through, then sift it over again in the next coarsest sieve, and so till the grains are fine enough; the last sieve, must be so fine that whatever passes through it will be too fine, for powder, and is to be worked over the next batch. As the paste will naturally roll together in large round balls, when worked in the sieve, a board must be made near as large in circumference as a common pewter plate, and about one inch thick, on the centre, declining to the edge, of some hard wood turned in a lathe, and made as smooth as possible. This board must be put into the sieve among the paste, which breaks the lumps in pieces, and forces the paste through the sieve.

When the powder is well grained in the manner directed, it must be rolled in a barrel, the inside of which is to be made as smooth as conveniently may be, with a small


door cut in one side capable of being shut tight, and the barrel to be fixed so as to be turned by the shaft of the mill. Put in a few pounds at a time, and let it be rolled as above, which will make the powder smooth; then sift it in the finest sieve, till the fine parts that work off in the barrel pass through the sieve, which is to be returned again into the mortars. The powder must be put in flat trays or dishes, and set by to dry either in a small room kept warm with a large stove, or, if the weather be dry, in the shining of the sun.

I, therefore, most heartily recommend to the good people of this Continent to enter into these necessary businesses with spirit, being well assured that a greater quantity may, with ease, be made than will be needed for our consumption, even admitting the times to be worse than the threats of the British Administration would lead us to expect.

Any person inclining to build a powder-mill will be shown a plan, with directions for the construction of all its parts and utensils, by applying to their very humble servant,