«j?s On the douhhs Imager caafect by ^imojphericcd RefraiKpn. 



aperture of the conical tube adapted to the tefcrvoir. A conftant ftrcam will then , 

 rife fo long as water below can fupply the tube *. 



I am, 



SIR, 



Your humble fervant, 

 Dalton^ Sept. I, 1800, W. CLOSE. 



My acknowledgements are due to Mr. Clofe for his obliging private poftfcript. In 

 reply to his doubt, left from the number of hydraulic inventions which have appeared in 

 this Journal, his contrivance might not be inferted ; it feems proper to obferve, that I 

 eonfider hydraulic works as of the bigheft importance to fociety, whether we look to a 

 fupply of the £rft neceflity for confumption, or to the advantageous ufes of neglefted,^ 

 though valuable, firft movers ; that thefe works muft in moft cafes be modified by, 

 localities and other circumftances } and, confequently, that the moft ufeful prailical 

 knowledge will not confift in an acquaintance with one or more of the beft engines, but 

 with that great variety of happy contrivances which reading and enquiry muft point out. 

 From reafons of this fort, when exercifing my duty as editor of a work rendered re- 

 fpedlable by the correfpondence and favor of learned and ingenious men, I have been little 

 felicitous of the abftraa comparative merits of the works I receive. If they contain 

 ufeful fadts, clear dedu£kions, or new profpedls tending to lead others to improvements in 

 fcience or the arts, they are certainly well calculated to form part of this mifcellany. — N. 



III. 



On double Images caufed by Atmofphetical RefraBion. By Wuuam Hyde Wol- 



LASTON, M.D. F.R.Sf. 



I 



N fome of the laft volumes of the Philofophlcal Tranfaflions, there have been related 

 many inftanccs of ftrong atmofpherical refra£lion, by which objcds feen near the horizon 

 have appeared inverted, and the horizon itfelf either elevated or depreffed. 



Mr. Huddart firft took notice of a diftant image, inverted beneath the obje£t itfelf y 

 and, m the Philofophlcal Tranfaftions for 1797 J, has defcribed feveral fuch appearances, 

 accompanied with an optical explanation, wherein he (hews, that the loweft ftrata of the 

 air were at the time endued with a weaker refradlive power, than others at a fmail 

 elevation. 



* See the experiments of Tenturl on the lateral motion of fluids, before quotedir—C.. 



-}■ Phil. Tranf. iSoo, p. 239. 



4 Or this Journal, I. 146. See alfo 12^5, and elfewhere, as by the index, 



3 In 



