in Fluids. 273 



which h acquired or parted with Heat, and the motion 

 was most rapid in those parts of the instrument where 

 the communication was not rapid. 



A partial motion might at any time be produced in 

 any part of the instrument by applying to that part of 

 it any body either hotter or colder than the instrument. 

 If the body so applied were hotter than the instrument, 

 the motion of the saline liquor in it in that part of it 

 immediately in contact with the hot body was upwards ; 

 if colder, downwards ; and whenever a hot or cold body 

 produced a current upwards or downwards, this current 

 immediately produced another in some other part of the 

 liquid which flowed in an opposite direction. t 



On inclining the cylindrical tube of the instrument to 

 an angle of about 45 degrees with the plane of the hori- 

 zon, and holding the middle of it over the flame of a 



* O 



candle at the distance of three or four inches above the 

 point of the flame, the motion of the Fluid in the up- 

 per part of the tube became excessively rapid, while that 

 in the lower end of it where it was united to the globe, 

 as well as that in the globe itself, remained almost per- 

 fectly at rest. 



I even found that I could make the Fluid in the up- 

 per part of the tube actually boil^ without that in the lower 

 part of it appearing to the hand to be sensibly warmed. 

 But when the flame was directed against the lower part 

 of the tube, all the upper parts of it in contact with the 

 liquid, and especially that side of it which was upper- 

 most as it lay in an inclined position, where the ascending 

 current was most rapid, where it impinged against the 

 glass, were very soon heated very hot. 



The motions in opposite directions in the liquid in 

 the tube were exceedingly rapid on this sudden applica- 



VOL. I. 1 8 



