8S ON THE SUPPOSED CURRENTS IN HOT LIQUIDS. 



the other, which occafions their reciprocal change of motion* 



Thefe air bubbles are of different fizes, hence the different 



velocities of the pieces of amber. 



Obs. 3. Th« 3. If the alkaline folution be made to boil for a few minutes 



amber acquires a in a ]afs veffe j and then f u f penc ied immediately in the air to 



higher tempera- ,,,,,% • r r • , . 



ture by boiling cool, bubbles or (team continue tor iome time to detach 

 than the folution themfelves in great abundance from the pieces of amber, and 



jtfelf, and con- r , .,» . ,. r . TT r 



fcquently it ge- occalion a very bnlk motion in theJe pieces. Hence we lee 

 nerates fteam. that the amber acquires a temperature higher than 212°, and 

 that it gradually parts with this excefs of caloric to the fur- 

 rounding liquid. 

 Obs. 4. Irre- 4. After all extrication of fleam ceafes, the amber con- 

 ffteT the fteam tniues to m °ve rapidly upwards and downwards in a very 

 has ceafed; fol- irregular manner. The rapidity of thefe motions gradually 

 fidencc/ U * diminimes, and when the folution has cooled down to about 

 140° (the air being 50°) the amber fettles at the bottom. * 

 Thefe motions are too rapid to be occafioned by the cooling of 

 the liquid, yet they are certainly connected with its high 

 temperature. I would have fuppofed that they indicated the 

 currents into which the liquid was thrown by boiling, as they 

 are extremely fimilar to what takes place when the liquid is 

 agitated violently, were it not that they laft much longer, 

 and that they always flop when the difference between the 

 temperature of the liquid and of the air is about 90°. 

 Obs. $. Afcent 5. After the amber fettles at the bottom, the cooling goes 

 oft earn er; Qn w j t j l0u ^ ; any thine remarkable till the liquid reaches the 



whence it is in* y o 1 



ferredthatit temperature of about 100° (the air being at 50°). At that 



♦ha 1 * th* fl^d ^ tem P erature f° me °f the a mber may be obferved fufpended 

 juft above the bottom of the veffel ; and, as the cooling ad- 

 vances, the amber gradually rifes higher and higher. No 

 motion can indeed be perceived, but if the fituation of any 

 individual particle be obferved at intervals, it will appear 

 evident that it has changed its place, and afcended nearer the 



* This experiment requires that the amber be in the ftate of a 

 pretty fine fand, otherwife it fettles at the bottom at the very firft. 

 But even then the currents may be diftinguifhed by the naked eye, 

 if the glafs venel be tranfparent. This faft is curious, and can 

 only be explained by fuppofing a greater interval than ufual be- 

 tween the currents and the reft of the water, or by fuppofing their 

 fpecific gravity to be different, 



furface. 



