I should before now have answered your esteemed favor of the 9th Feby last, but I wished to communicate something relative to the Looms: I find nothing yet worthy of your attention.—

I have made several Enquiries relative to the mode of lining the Cisterns for Water. In the West Indies where Pouzzolane abounds, they plaster them in the inside with this Substance mixed with lime & sand, and it has the peculiar quality of becoming as hard as stone by Water: so that immediately after lining them they may be filled with water, and the iron which is contained in the pouzzolane, by the action of the Water forms a perfect stone, impermeable to water, and there seems to be no end to its duration. The Roman Baths are made in this way, & were found to be as perfect after the lapse of centuries as when first made.—If the turnings of the Cannon, obtainable here from Foxall’s Foundary were to be mixed in a small quantity with mortar I am confident that the decomposition in consequence of its contact with water would produce as perfect a cement as could well be formed; and when the waggons or Carts come with the library I can send you some. It will not take much to line your cisterns. But I have heard also of another cement, that is said to answer perfectly, and it may be immediately tried.—I have such evidence of its answering that I cannot doubt it. Let good mortar be made of two or three parts of sand to one of good stone Lime. Let it stand in a heap till hard; then break it down again, and let it be well beaten with molasses, of which it will not take a quart to a Bushell. This is to be plastered on immediately, & it will be stiff enough to make a good plaster; but it must be laid on in a thin coat, which must be suffered to dry sufficiently to lay on another coat which will fill up every small crack or fissure in the first, and it will make a firm and solid piece of work.—The Molasses becomes a kind of resin, being compleatly changed in its nature, and sometimes it has been used for plastering the outside of buildings, giving a yellowish warm hue when mixed in the proportion of about one gallon to 30 of white wash or the water wth which rough-cast is formed.—

I shall now describe the filtre.—I invented it above twenty Years ago.—I had purchased some very fine rich Cyder, & being advised to filter it through Sand, I put the Cyder through a Cloth, & let it fall gently on Sand, put on Straw, to keep the bottom holes of the Vessel open. In a very short time I found that the mucus contained in the Cyder, filled up the interstices of the Grains of sand, & the Cyder instead of filtering through stood on the Surface. To prevent this, I contrived a Cask, filled, within some Inches of the top, with Strata of rough pebbles, finer gravel, rough & fine Sand, the roughest at the bottom, and gradually increasing in fineness to the top.—Over this Cask or Vessel on an inside rim, I place another Cask covered with fine netting, or Haircloth, such as is used for Sieves, to prevent the gross impurities, or the pomice of Cyder &c to pass, & a Tube carries the Liquor from the bottom of the upper Vessel, to the bottom of the lower Vessel, which Tube enters between the bottom of the lower Vessel & a false bottom pierced full of holes.—The Cyder or Liquor being put into the upper Vessel enters between the true & false bottoms of the lower Vessel, & rising through the different Strata of Gravel & Sand, runs off, pure, through a cock placed some distance from the top of the Sand, & with the velocity of a descent of Water falling from the upper Vessel through a Tube whose exit would be as much below the upper Vessel as the Cock is placed. Care must be taken that this Cock be wide enough to carry off the liquor as fast as it rises.—If the Sand should boil up the Cock should be placed further from it, or a Hair-Sieve may be put immediately on the Sand. To render the Water perfectly sweet it may be passed through a Vessel filled with fresh1 Charcoal, and to render it perfectly cool, it may be let down from the filtering Vessel into a Well or Cistern and remain there in a vessel of Tin, or Earthen Ware with an inverted Syphon to draw it off when wanted. On the next page I will explain the whole by a drawing.—