Circulation of a Fluid refinibling ff^inJ/, jtj 



-ttoned cotourlefs oil Being imperfedly congealed, an attempt was made to caufe radiant heat 

 to defcend through its mafs. It was expefted that the tranfparent or nrelted portion of the 

 oil would in this cafe have been hemifpherical, or at ieaft of fome convex figure ; but this did 

 not happen, for the furface beneath the fluid or mel;ed part continued flat. Whence the 

 Count infers, that the fufion was eftefted merely by the heat abforbed or generated by the 

 fides of the tumbler. 



7. The concluding experiment of this ElTay affords a ftriking rcfult of the circulation oif ' 

 fluids under difierent circumftanres. When the inflrument dcfcribtd in our Journal, I. 342, 

 was placed by accident in the window of a ruom warmed by a German ftove, the difference ■ 

 of temperature, on the fide neareft the window from that oppofite the internal part of the 

 room, was fuch as to keep up a conftant circulaticm of the fluid. This event induced the 

 Count to fubifitute a box of plate glafs in the place of one of the panes of his window. This 

 apparatus, which was 13 inches high, 10'- inches wide, and one inch wichin from plate to 

 plate, was half filled (and as I ibppofe afterwards completely filled) with the faline folution. 

 with pieces of amlcr floating in it, r.s dcfcribed at the place laft quoted. The Count ex- 

 pelled to behold the currents as ufual in this new vefl'el ; but to his great furprife they 

 proved not vercical, but horizontal, exhibiting a<5lual winds in oppofite directions, which 

 fpringing up in the d,fRrent regions of thia artificial atmofphere, prevailed for a long 

 time with the utmoft regularity, while the fmall particles of the amber colle^ing them- 

 felves together formed clouds of the moft fantaftic forms^ which, being carried by the winds 

 rendered the fcene perfectly fafcinating. 



Several fubordinate circumflances gave thefe motions a more intimate refemblancc to 

 the atmofpherical phenomena. One remarkable appearance never failed to prefent itfelf 

 regularly every day during the three weeks that the experiment was continued. The cloudsj 

 after having been driven about all day by the different currents, in the liquid (of which there 

 were fimetimes as many as fix or feven running in oppofite dire£tions at the fame time), 

 never failed to colle£l themfelves together in the evening into large mafTes, fometimes form- 

 ing only oncy and fometimes two or three ftrata at different heights, where they remained, 

 to all appearance perfectly motionlefs during the night. 



The experiment was put an end to by the accidental breaking of the veffel. 



VI. 



^n Account of certain Motions which fmall lighted Wicks acquire when fwimming in a Bafon of 

 Oil; together with Objervations upon the Phenomena tending to explain the Principles upon 

 which fuch Motions depend. By PATRICK WlLSON-, F.R.S. Edin,, and Profejfor of 

 pra£lical jijironomy in the Univerfity of GLtfgo-ut *. 



DE4K SIR, Glafgow College y Jpril 28, 1 795; 



Jl now fit down to give you fome account of the little hydroftatical lamp which I fo- 

 briefly mentioned to you in a former letter. As I am far from being fure whether what i 



• In a Letter, to Mr. John Playfair, F. R. S. Edin. &c> infertcd in the Edinburgh Tranfaftiont, vol. iv. 



