FRANKLIN, Benjamin (1706-1790). AUTOGRAPH LETTER SIGNED ('B. FRANKLIN') TO LORD KAMES, London, 28 February 1768, wondering if his 'long letter, I wrote him about this twelvemonth, on the Subject of the Disputes with America, did miscarry, or that his Answer to that Letter miscarried' [see letter of 25 Feb. 1767 above]. In response to Kames' complaint of Neighbour Smoke, he tries to explain its causes and discusses at length the law of nature 'whereby whenever the outward Air is warmer than the Walls of the Vent, the Air included being by those Walls made colder, and of course denser and heavier, than an equal Column of the ouward Air, descends into the Room and in descending draws other Air into the Vent from above to supply its Place; which being in turn cooled and condensed by the cooler Walls of the Vent, descends also, and so a current downwards is continued during the Continuance of such difference in Temperament between the outward Air and the Walls of the Vent'. He continues in great detail about the influences of the season and outside temperature and offers a remedy against the smoke. Franklin proposes also that Kames obtain a 'Philadelphia Grate', as long as it is 'one that is rightly made, and ingenious workman to fix it properly'. He refers to instructions for sliding chimney plates, that he had sent to Sir Alexander Dick. (A copy of Franklin's letter to Dick is included with the lot). Subscribed 'With sincere Esteem & Respect, I am my dear Friend yours most affectionately', 3 pages, folio (322 x 201mm), (margins reinforced; folds of second sheet strengthened, not affecting letters and in very good condition); with autograph wrapper and seal (torn and mounted on paper). At the beginning of this letter, Franklin discusses his idea of happiness, which he believes 'consists more in small Conveniencies or Pleasures that occur every day, than in great Pieces of good Fortune that happen but seldom ... Thus I reckon it among my Felicities that I can set my own Razor and shave myself perfectly well, in which I have a daily pleasure, and avoid the Uneasiness one is otherwise oblig'd sometimes to suffer from dull Razors, and the dirty Fingers ... of a slovenly Barber'. In this letter Franklin also demonstrates his gift for scientific exposition, but more particularly his inventiveness. He has invented sliding chimney plates, 'as they keep a Room sufficiently warm, are simple Machines, easily fix'd, and their Management easily conceiv'd and understood by Servants'. For this purpose, Franklin arranges that the copy of a letter he had sent to Sir Alexander Dick, explaining the system of chimney plates 'after more than 20 years Experience of my own Contrivances and those of others for the warming of Rooms', be forwarded to Lord Kames. This letter goes into great detail about the theory and practice of these sliding plates and the proper method of fitting them. Published in The Papers of Benjamin Franklin, ed. L.W.Labaree, vol.15 pp.60-62. The 'Philadelphia Grate' is also discussed in Franklin's Experiments and Observations on Electricity. 4th edn., 1769, pp.248-318. Included with the lot: Benjamin Franklin. Letter to Sir Alexander Dick, London, 21 January 1762, scribal copy, copied without address or subscription, 3½ pages, folio, endorsed on verso of second sheet 'Copy Letter from Dr.Franklin about his Chimney Machines'; with wrapper and seal, addressed to Lord Kames (torn and mounted on paper). Published in The Papers of Benjamin Franklin. vol.10 pp.13-16. (4)