52 



AEROStATIC VOYAGE, 



With refpefl to the common notion that experiments on i\?^ 



it is alto- 



to each other, 

 unfounded and 

 unpradlicable* 



The common 



and°wlter being ^^P^^'^^ ^^ '^® ^^^ made by mixing it with water, 

 direftly applied gether falfe in the cafe of Dr. Irvine. No doubt this may be 

 done theoretically. It is eafy to fay that ice lofes fo many de- 

 grees which heat water only fo many. But then no ice muft be 

 mehed, which if not impoffible is extremely difficult, or what 

 is equally fo, the quantity melted muft be found, and an al- 

 lowjtnce made for the latent heat, which is itfelf not precifely 

 afcertained, at leaft not with fufficient accuracy for this pur- 

 pofe. I have only to add that this gentleman's enquiries would 

 have been earlier noticed if I had been informed of I'lem, 

 which I was only a few days ago. 



W. IRVINE. 

 April, 1805. 



XII. 



Short Account of fome of the mofi remarkable FaSis andOhfcrva- 

 •vations in an Aerojlatic Voyage, made from Fettrjburgh, by 

 Meffrs, Robertson and Sacharoff, under the Sanction 

 of the Imperial Academy, W. N. 



,.T, 



Aeroftatic voy- JL HE notice of an aeroftatic voyage performed by Meflrs, 

 J^^/^°"*^*^"^"Robertfon and Sacharolf from Peterfburgh, under the diredion 

 of the Imperial Academy of Sciences, June 30, 1804, of 

 which an abridged account was given to the National Inftitute 

 of France*, is very interefting, from the fcientilic views and 

 conduct of the managers Lowitz and Robertfon, as well as 

 for Its other particulars. 

 Afcent of the Their balloon was a fphere of 30 feet diameter, and role 

 obferTerl! ^^° at a quarter paft feven in the evening, with the afceniional 

 force of one pound, the whole weight of folid matter (includ- 

 ing 110 pounds of fand for ballaft) being 622 pounds. When 

 they were over the river Neva, at the elevation of 108 toifcji 

 or ^20 feet, they defcended a little by the condenfation of 

 the gas; but rofe again bv throwing out a little of the ballaft. 

 The ufual phenomenon of a flow rotation of the balloon pre- 

 fented itfelf, which doubtlei's arofe from the unequal aftion of 

 the air againft an irregular furfuce, as we fee in moft other 

 bodies rifing or falling in a Hiiid. 



♦ Inferted in the Annalcs de Chimie, LH, 121. 

 1 But 



