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Show 53o Concluding Remarks flom M. Mairan. De Luc's Account of the mines in the Hartz {crel't in Germany, alfo Bergman's Phyfical Gc "graphy; and Mull'chenbroek's Introduétio ad Phil. Natur. attic. 2299. E.] . [M.P.] The Author's Epitaph on Himf elf. 53x .s lingular per borate and important. I: pollibly \. "5* m iriperiixle the neecihty of this theor thatDr. Franklin has {it ‘ let: A caulc lot the frequent :tp'uearu I: of the auroras at the affirva . . - zit.r: and I find by A". in's table, that out of 1441 auroras ~ : c, recorded during 1163 years. 212 were [can in the months or October, and 202 in The body Of BENJAMIN FRANKLIN, Printer, thofi: of March ; which gives the preference to Ottober, contrary to Mullflmnbroek, and conformable to Dr. Franklin.» , Mairan alfo makes it Clear that the auroras wereformerb' 11w} my‘hyumz ; infomuch that the number which appeaer from 1722 to 1751 inclufively, (amounting to 989 in only 30 years) more than doubles according to his table thole that had appeared during the (pace of1138 years before-He {cams alfo to ham proved that the aurora; are neither perpetual, ancient, nor unu'lually brillian. towards the high latitudes in this norllm-n hemifphere; and that they are perhsps ne- ver feen in it at {0 low latitudes as 36 ".-In the/barber}: hemifphere, he confirms their appearance from Ulloa; who lent him a very {atisfaé‘tory account by letter, of fome that he had teen in doubling the [and at Cape Horne; and Frczier allo appears to have feen the like in the fame lituation.-Re{pctting the berg/2! ofthc auroras, he exhibits a computation made by various philofophers in various man- (Like the cover of an old book, Its contents torn out, And fiript of its lettering and gilding) Lies here, food for worms ; Yet the work itfelf {hall not be loft, For it will (as he believed) appear once more, In a new And more beautiful edition, Corrected and amended ners of certain particular ones, and llates the average of them at 175 leagues high (of which leagues :5 go to a degree) ; the lowelt being 47 leagues, and the highell 275 leagues: And in another place he By computes the average of them at 200 leagues high, which is 8 degrees or 556 Englilh miles. See Mairan, p. 554.; 547-554; The Author *. 82-93; 379-339; 104) 437; 438-44" 56-7: 405-6412, 433-6: alfo Newton's Optics, Q. 28. To conclude; when I firfi read the above paper in May lall, I thought I {aw true principle: contained in it, though I felt difficulties In their application. Upon adue confideration however of the locality of the auroras, the irregular periods of their appearance, and the imall elevation of the atmofphere; I find thefe difliculties to be in- '‘ [A news-paper . , in whichIhave [can this copyo f D r. Franklmc ' ' :pztap/a on [um/H , rays that it firlt appeared in 3 Ba on cftabhfhed and printed by Dr. Franklin. E] ' fl "1W paper fupcrable. I have therefore applied the fame principles of " e/eflri‘ ‘ c.1111} (burger! air, and a )zmz-(anI/ufling tart/J," to another hypothefis; which {eems to admit a nearer approximation to the truth. For va- nous reafons however, Imake no alterations in tne notes; which tend to cliablifh two lingular facts; viz. [hat the air is muilt and warm at unexpected heights above, and that the rartb is frozen at unexpected depths below. july 1779. NB. Vida Addenda. {111% e Yyyz APPEN- -Il ill lIlllllilill‘l‘W |