When fwimming in {i h J S N of I L^ Sec. 167 



prefTed upwards by a force fufEcient to raife part of it above the 

 general level. But this heated portion of oil, in its endeavour- 

 thus to rife up, will meet with a refiflance equal to the weight 

 of the incumbent lamp, which will determine it, in feeking a 

 vent, to Aide out from under the bafe in a thin fuperficial Jlream\ 

 and it feetns to follow^ with equal certainty, that this conftant 

 flream will flow moll readily and mod cbpioufly towards that 

 fide of the bafe of the lamp where the refiflance is lead, or where 

 it has the fhortefl way to prefs forward ; that is, from under 

 the wick or flame, to the edge of the bafe which is the nearefl, 

 according to what we have feen to be agreeable to the pheno- 

 mena. But, from the laws of motion, it is certain, that the re-* 

 ad;ion of this flream of rarified oil, thus iffuing mofl rapidly 

 and mofl copioully from a particular fide of the bafe, mull im- 

 pel the lamp in the contrary dire<5lion, and make it fail in the 

 manner we have feen. It may further be remarked, that the 

 heated oil, fo retreating from the flame, and endeavouring to rife 

 fomewhat above the general level, in confequence of its dimi- 

 nilhed fpecific gravity, may more or lefs lift up that fide of the 

 bafe nearefl the wick, and aid the rea(5lion of the recoiling 

 flream, by making the lamp fail in the oppofite diredlion, as it 

 were down-hill. 



That the rarified oil under the bafe has really a conftant 

 tendency to fife above the general level, feems undeniable, from 

 the following fadls, namely^ that after any of the lamps has 

 burned a little while, and has got its bafe foaked with the oil, 

 as foon as the flame is blown out the lamp finks to the bottom j 

 and even a lamp, with its bafe made of a thin lamina of talck, 

 fails very well till the flame is extinguifhed, and then it imme- 

 diately finks. 



Agreeable to the explanation which has now been attempt- 

 ed, I found, that when a topical heat was applied to the furface 

 of the oil, by bringing the point of a poker, dully red hot, near- 



