153 ON THE PASSAGE OF HEAT THROUGH FLUID9. 



rature of the air of^the room. One ounce of olive oil heated 

 to 1 40° was poured on a fmall piece of card, fufpended on 

 the furface of the water, and the card was flowly withdrawn. 

 Any motion of the water was thus avoided. In the courfe of 

 a minute the thermometer began to rife flowly, in live minutes 

 from the commencement of the experiment it had rifen four 

 degrees, in ten minutes 6f , in fifteen minutes eight degrees. 

 It then became ilationary, and continued fo for feven minutes 

 before it began to fall. Its defcent was very flow. 

 II. A brafs ball Experiment 2. Into the veflel B, water at 49° was again 

 heat I dcwnwards!P oyre ^ , ^ ^ covered the bulb of the thermometer one inch. 

 A brafs ball 1 \ inch in diameter, was heated to 212 in boiling 

 water, and fufpended over the bulb of the thermometer by a 

 wire, previoufly adjufted fo as to be diftant from it \ of an 

 inch. For 2§ minutes after immerfion of the ball, the ther- 

 mometer did not feem to be affe&ed, in five minutes it had 

 rifen a degree and a half, in ten minutes from the commence- 

 ment of the experiment 4-f, in 15 minutes 1\ t in 20 minutes 

 8 J degrees. It then became ftationary, and did not begin to 

 defcend till 15 minutes more had elapfed. By fufpending a 

 thermometer reprefented by C in Fig. 1 . fo that its bulb was 

 merely immerfed under the furface of the water, the rife of 

 temperature in the fluid in contact with the bulb was found to 

 be in a few minutes 82, from which point it again defcended 

 gradually. 



It may perhaps be more fatisfa&ory to have this latter ex- 

 periment ftated more minutely in the form of a table. 



Temperature of the air of the room, and of the water in the 

 veflel 49°. 



In 3 minutes after immerfion of the heated ball, 



Therm. A 49| Therm. C 78 



5 min. 

 10 



15 - 



20 



30 ----- 



40 - 



50 



65 



On repeating both thefe experiments iimilar refults were 

 obtained with variations fo inconfiderable as not to affccl their 

 accuracy. 



In 



