Emboldened by the friendship, and mark’d attention, you have always shewn to those who have attempted to improve any of the useful arts, I, though an utter stranger address you, and if you can spare as much time from those things that concern the greater interests of the land, I shall not doubt but that He who hath so considerably enlarg’d the bounds of Science, will attend, with some degree of complasancy to even a very feeble essay of the same kind. It is but candid to acknowledge that when balloons were first heard of in this country as a discovery made in France I became an enthusiast enough to believe they would one day become useful though this opinion hath always been contradicted by those in whose wisdom I had the greatest confidence. The appearances that the greatest and most useful improvements have put on at first, seemed so strikingly realis’d, that my thoughts have been ever since much imployed in enquiries the principle object of which, were to obviate the most Gigantic of the defects that hath hitherto set the discovery at so great a distance from utility: bulke which renders them unwieldy, and their flimsy texture so extreemly liable to accidents, ever difficulties that to my mind always appeared insuperable, both of which I flatter myself I have remov’d, but my situation in the country rendering actual experiment unattainable, I beg leave so far to tax your patience, as to state the principles, and your time to say whether they are founded in philosophical facts. Vapour by filling space, expels it without other force than that of heat the atmosphere, which when again real[ ]by condensation to water, fills but a small part of the space it did when under the modification of vapour, its actual weight is however equal to itself and is the same whether under the different manifestations of steem or water, either of which are equal to that quantum of air which the same quantity of water, when rarified to steem will fill up. Hence it appears plain that if vapour will condence where air cannot be admited to fill up the space, and in the form of water, can be extracted without admiting air, the vessel will be bouy’d up by a force equal to the weight so much of the common atmosphere as will fill the solid content of the vessel. I will now describe the mechanical operations that I conceive will procure these effects. A Globular Balloon of either cast Iron or Brass, from one side of which a tube projects, which communicates with the inside of the Balloon, through this tube and close to the Balloon is a cock, which when turn’d, will make the Balloon air tight, at the extremity of the tube, is another cock of the same kind, the solid content of the tube between the two cocks, must be sufficient to contain the water that is formed by condenceing all the vapour contained in the Balloon, the most simple mode of filling which with steem, would I think, be, by filing the Balloon with water, up to the mouth of the tube, then stoping it by puting the hand on it, to prevent the water from issuing out, while the Balloon is turned upside down, and the mouth of the tube placed in a vessel of water underneath (which will by a well known experiment remain suspended) until by heating the water in the Balloon above, as well as that in the vessel below, until the Balloon instead of water is entirely filed with steem—the cock at the extremity of the tube being now turned, the vapour in the balloon becomes thereby enclos’d and the air prevented from rushing in, when the steem in the balloon is sall? all be condenced, which I concieve will be a natural consequence as soon as the balloon becomes cold, which being now turned with the mouth of the tube down, the water from gravitation, will naturally fill up the tube to the cock next the Balloon, which being now turned, and the one at the extremity of the tube being turned back to let out the water, now between the two cocks, the vacuum becomes complete if the pores of the Balloon are not pervaded by the atmosphere, provided the above principle be just, the Balloon will asscend with force greatly superior to that of air in water

I am Sir with profound veneration Yours