1806.] 



Proceedings of Learned Societies. 



*15 



folving a final! quantity of |;;um arable in 

 ■it, dill largei- fphciules of mercury were 

 fupported at the furface of the liquid. 



" The experimeats I'ucceed equally well 

 wiien oil is poured on the water iuftead 

 «f ether, but thev will not anlwer with 

 alcohol. In order to examine the kind 

 of riini which is formed at the furface of 

 the water, the following exiieriment was 

 made: Into a cylindrical glafs about an 

 inch and a half in diameter, and ten 

 inches in height, was poured fome very 

 clear water to tlie height of nine inches. 

 On thg water was placed a ftrataiu of ether 

 a quarter of an inch thick, a umnber of 

 fmall folid bodies, fucli as a fph.erule of 

 mercuiy, fomc pieces of extremely fine 

 tilver wire, and a little powder of tin 

 which remained fufpended. They con- 

 tinued in tlie fame ftate after the veHel 

 bad been turned round on its axis feveral 

 t:;nes with conUdt-rable rapidity. All tlie 

 linall bodies fufpended at the furface of 

 the water, turned round along with the 

 glafs and (topped when it was flopped : 

 but the liquid water below the furface 

 did not at tirlt, begin to turn along with 

 the glals, and its motion of rotation did 

 not ceafe all at once upon Hopping that 

 of the velfel. In fact, all the appearances 

 Jliewed that there was a real pellicle at 

 the fm-face of the water, and that this 

 pellicle was ftrongly attached to the fides 

 of the glals fo as to move along with it. 



"Upon examining with a good inagniller 

 through the liratum of ether, the iinall 

 bodies whicli were fupported at the fur- 

 Ikceofthe water, the exil'tence of this 

 pellicle could no longer be doubted ; 

 more particularly when it was touched 

 with the point of a needle. For in this 

 safe all the fmuU bodies v.ere obferved to 

 tremt)lc at the fame time. 



" Having left this linall apparatus at re- 

 pofe in a quiet chamber until the Uiatuin 

 of ether was entirely evaporated, 1 

 •xamined it again «ith a magnirier. The 

 furfjice of the water was prccifely in the 

 iainc fiate ; the fmall folid bcsdics were 

 ftill tjivrc, "in the fame lituatiop, and at 

 die fame dilinncci from each other. , 



" V-'\t n this experiment was made with 

 R cyliiuirical glafs of much largei- diame- 

 ter, the etFects of the adheiion of the pel- 

 licle of the water to. the lidcs of the vef- 

 fcl, were mucii iels fonlible, with regard 

 ro thofit; paits of the fame wiiich were 

 iituated near the axis. It was diiiicult to 

 liievent tiic fiiiall bodies whicii Hoatcd on 

 tiie fui-face of the water from uniting, and 

 !whcii united thev often formed mutfes 

 itjii heavy to continue to be fupported; 



and having broke the pellicle of the iva- 

 tsr, they fell to the bottom of the veflel. 

 If the particles of water adhere Itrongly 

 to each other, it appears as a ueceflary 

 confcquence that a kind of pellicle will 

 be formed at the furface of the liquid. 

 When a fmall folid body placed on the 

 furface of water, becomes wetted, it im- 

 mediately defcciids beneath the pellicle. 

 Then the vifcidity of the water begins to 

 manifelt itfeif in a ditferent manner, but 

 With much lels eft'ect tlian when it utts at 

 ths boundaries of the liquid. 



" With a view to render fenfible the re- 

 fidance which the pellicle of the inferior 

 furfaco of the llr.itum of water oppofes to 

 a folid body which pa'Jes through that 

 liratum falling freely downwards, the fol-, 

 lowing experiment was made. Having 

 tilled a wine glafs to about half its liei'ght 

 with viM-y pure mercury, a tiratuin of wai- 

 ter a quarter of an inch thick was poured 

 upon !t, and upon that a Itratuin of ether 

 one-fixth of an inch thick. When the 

 whole was at rell a fpherule of mercury 

 was let fall through the ether, which, be-. 

 ing too heavy to be fupported by the. 

 pellicle at the fuperior furface of the wa- 

 ter, broke it, and defcended ; but upon it*, 

 arrival at the inferior furface it vvas {loo- . 

 ped, and remaincfl there preferving itg, 

 iiellicle form. It was no doubt the pel- 

 licle of the inferior furface of the water 

 which prefentcd this contact, and as this 

 pellicle was fupported by the mercury it 

 is not furprilingthat it could fupport with- 

 out being broken, a fpherule of mercury 

 much larger than the pellicle of the fuijg 

 rior furface could fupport. The exper'- 

 inent was then tried with a folution of , 

 gum arable in water in the place of pure 

 water. And it was found that much larger 

 fpherulesofwater were fupported when the 

 vifcidity of the water was thus increafcd. 



" To prove this fa6t in another mauner, 

 the experiment was varied by placing a 

 liratum of eth.er immediately upon the 

 mercury. The particles of this liquid ap- 

 pear to liave verv little adhclion to each 

 other; fur which reafon it was imagined 

 that the kind of film th'dt would be farmed 

 at its furf ice, mult have very little force. 

 The rcfult of the experiiaeut fully con- 

 firmed this conjecture. 



" Tlie very fmalled fpherules of mercury 

 let fall through this liquid feldoin failed 

 to niit immediately with the mufs of 

 mercury on arriving at its furface, where 

 thev entjrely dilkppeared ; and th.e Count 

 never fucceeded in cauiiiig cither a fplie- 

 rule of merciir,-, or the iinalleil metallic 

 pmtick', nor any gther ^'^dy gf greater ; 

 fpeciilc 



