16. This I fixed in a Brick Stove in my Garden, with its upper End fixed to a Vessel, which contained 45 Gallons of Water. I found the Event of this first Trial to be as follows, viz. When the Water run full Bore, at the rate of a Gallon in 17 Seconds, the Heat of the Water was found, by a mercurial Thermometer held in the Stream, at the lower End of the Pipe, to be 80 Degrees above the freezing Point, 180 Degrees being the Heat of boiling Water. When by means of a Turn-cock, a Gallon of Water was two Minutes in running, then the Heat was 140. At which Rate the 45 Gallons would be an Hour and half in running thro’ the Iron-pipe; at which Rate 25 Gallons will run thro’ in 50 Minutes, with so considerable a Degree of Heat; and if it was an Hour running, the Heat would approach still nearer to a boiling Heat, when first put into the Still, which would forward the Distillation if wanted.
17. I pumped the heated Water up again into the upper Vessel; and thus continued to circulate the heating Water, till its Heat was 160 Degrees in the upper Vessel, viz. within 20 Degrees, or one-ninth of boiling, the Heat requisite for plentiful Distillation. I was in hopes that if the Water in the upper Vessel could have been brought to a due Degree of Heat, and a Still-head were fixed on it, with its cooling Worm-tub, then Water might have been distilled in Ships, by having the Iron Worm-pipe fixed in the Chimney of the Cook-room: But I found, that when the Heat of the Water in the upper Vessel was 160 Degrees, viz. within one-ninth of boiling; then in running through the Iron Worm-pipe again, it was so over-heated, as to expand in the Pipe, into an explosive Vapour, which hindered the running of the Water. However I thought it not improper to give an Account of this Attempt, notwithstanding it failed. Not knowing whether this Method of heating Water, may not in some Cases, at Land at least, be of use, thereby to save, in some degree, both Fuel and Time: Perhaps an Iron Worm-pipe of a larger Bore might do better.
18. The Waste of Fuel will be less in proportion to the Quantity distilled in large, than in small Stills; and the wider the Still-head is, so much the more Liquor will be distilled, and more with a Worm-tub than without it. The Worm-tub may be so covered, as to prevent the flowing over of the Water by the Motion of the Ship.
19. It is of great Importance to take care to keep all Parts of the Still clean, that there may be no Rust or Verdigrease in the Copper, which will occasion Vomiting.
20. If it be necessary, the better to close the Joining of the Still-head, it may be done with a Lute or Paste made of a Mixture of powdered Chalk and Meal, wetted with Salt-water.
21. Now that several effectual Means are discovered, to make distilled Sea-water wholsome, and also to distill it in much greater Quantity in the same Still, in the same Time, and with nearly the same Quantity of Fuel; it is reasonable to believe, that it will be of great Benefit to Navigation, not only in saving much stowage room, for other important Purposes; but also in procuring fresh sweet wholsome Water, instead of stinking putrid Water, hitherto used; which must needs have a Tendency to promote that putrid Distemper, the Scurvy. And if withal due Care be taken, to exchange for fresh Air the putrid close confined Air of Ships, which has occasioned the Death of Millions of Mankind; then Navigation will become remarkably more healthy, and with little more Danger to Health and Life, than at Land, except from Storms.
22. Now supposing, that in a sixty Gun Ship, the 110 Tuns of Water, for four Months use, were distilled at the Expence of three Bushels of Coals to a Tun, this would consume nine Chaldrons of Coals: And as a Chaldron of Coals weighs about a Tun and half; hence it appears that Coals will distill about eight times their Quantity of Water. And the 110 Tuns of Water weighing (at the Rate of 2240 Pounds to the Tun) 138 Tuns; and the nine Chaldrons of Coals weighing thirteen Tuns and half, that is 94 Tuns and half less than the 110 Tuns of Store-water; and allowing twenty-four Tuns and half for the Still, Water-casks, and Coals, there will be 70 Tuns Weight of Stowage saved thereby for other Uses. Or if some Tuns of Store-water are carried by way of Precaution, which it will be advisable to do, especially at first, till they can be assured, by repeated Experience, what Quantity can be depended upon by Distillation; even then about half the Tunnage will be saved, which will be a very material Advantage.
23. Tho’ when the distilling Liquor runs from the Bottom of the Worm-pipe, thro’ a long Pipe fixed to it, the Waste by the ventilating rushing Air, is not great when the Water in the Worm-tub is not hot; yet the following Precaution, if needful, may be used, in distilling by Ventilation, viz. to fix at the lower End of the Worm-pipe, by means of a wooden Fawcet, a small Cask for a Receiver; the Fawcet to enter the upper side of the head of the Cask, and in order to give a free Passage for the great Quantity of ventilaing Air to pass off, and withal at the same time to prevent the escaping of much moist Vapour with it, it will be proper to fix at the Bung-hole a long upright Pipe of Wood, or of any Metal. I used a Gun-barrel four Feet and a half long; through which some small Degree of moist Vapour escaped; as appeared by the Dampness of a Piece of Paper, fixed at a little Distance above the Mouth of the Gun barrel. This Vapour became visible, and much increased, when the Water in the Worm-tub was very hot; at which Time, less is distilled into the Cask-receiver; then also there is more Danger of the Spirit of Salt arising. And it was observable, that the Water in the Worm-pipe Vessel heated much sooner by Ventilation, than in the common Way of distilling. For which Reason that Water ought to be changed so much the oftener, which can easily be done at Sea. The Cocks also at the Side of the Worm-tub ought to be large, in order to let the hot Water off the faster.
24. But tho’ the Water in the Worm-tub was sooner heated by Ventilation, because a double Quantity of hot Steam passed thro’ it, more than passed thro’ it in equal Times in the common Way of distilling; yet in the usual Way of Distillation the Liquor in the Still is hotter, with equal Fire, as is evident by its aptness to boil over thro’ the Worm-pipe; whereas in the ventilating Way it did not boil over, notwithstanding a very hot Fire was purposely made for a Trial. The continual Streams of ascending fresh Air, not only in some Degree abating the Heat of the Water; but also incessantly carrying off the more rarefied Particles of the Water, which, when expanded into a repelling State, do thereby cause the overflowing Ebullition of the Water. On which Account it is probable, that less Spirit of Salt is formed and raised by Ventilation than without it. As also on account of the fresh Air ascending, not from the Bottom of the Still, where is the greatest Plenty of Salt, especially towards the latter End of each Distillation; but about three Inches from the Bottom, viz. principally from the many Holes at the Surface of the Air-box.
25. And whereas the Quantity raised from the Still, and distilled into the Cask-receiver, cannot be seen; the proper Quantity to be distilled in each Distillation, may with great Accuracy be known, by having a well closed Pewter Bottle of the Size of about half a Pint, with a Brass Wyre as big as a Goose Quill fixed to it, the Wyre to pass thro’ the Receiver-cask, near the Bung-hole, which the floating Pewter Bottle will raise up, till the Marks on the Wyre appear just above the Cask. I made use of a Glass Viol for this Purpose. This Wyre will rise and fall freely, notwithstanding the Motion of the Ship, if it passes not only thro’ the Wood of the Cask, but also thro’ a metaline Pipe two or three Inches long, fixed in that Hole. And it will be known by the simmering or boiling Noise of the Water in the Still, whether it is hot enough to distill; for the running of the Water into the Receiver-cask cannot be seen.