rcfpeEling Heat or Caloric. 315' 



charge the air, that thermometer funk to nine degrees hclow 

 the temperature of the room, or fix teen degrees below the 

 point to which the other had been raifed by the expreflld 

 heat. 



It cannot be urged that in this experiment the air paffed 

 immediately from the fyringe into the air-veffel, for it had 

 to traverfe a tube interpofed between them of about four feet 

 in length. 



Now, when it is confidered that the thermometer was in 

 contact with the veffel B in only one minute point (for the 

 tube in which it was inferted, and againft the fide of which 

 the bulb refted, was more than three times the diameter of 

 the bulb), and that the whole furface of B was above 50 

 fquare inches -, and when it is alfo recollected that only a 

 fmall portion of the effecl: which the air iffuing from D was 

 capable of producing could manifeft itfelf by means of the 

 thermometer expofed to its a&ion (as the thermometer was 

 •obliged to be kept at fome diftance to prevent its being 

 broken by the difcharge of the air); fome idea, though not 

 an adequate one, may be formed of the mafs of heat that 

 muft have been thrown off from the whole furface of B in 

 the procefs of charging that veffel *. 



The. 



* Subfequent to the delivery of the prefers paper to the Society, I received 

 Air. Mufhet's interesting communication, which was afterwards inferted 

 in the Philofophical Magazine for February 1S00. It contains fotne cu- 

 rious facts which confirm and illuftrate the refults obtained from this ex- 

 periment. Speaking of the effects produced in the blaft-furnace by the 

 nature, cempremon, and velocity of the air ufed, he obferves that the com- 

 preftion always occalions an increafe of temperature. On entering a blow- 

 ing cylinder immediately after flopping the engine, he finds the thermo- 

 meter rife from 15^ to 17^.° higher than the furrounding atmofphere. A 

 thermometer held in the middle of the current of blaft was found to be 

 reduced below the common temperature as much as the cylinder was 

 .raifed above it. In fome cafes, when the common temperature is about 

 54 , the blaft, as it iffues, will fink the thermometer 2 or 3* below the 

 freezing point. 



He ftates another fact (fee alfo Mr. Roebuck's paper, Philofophical 

 Magazine, Vol. VI. p. 324.), which completely dots away every idea of 

 any part of rhe effect being derived from friction. At fome iron works 

 air-vauits of from 6o,o>:>t« 70,000 cubical feet in content are employed for 



the 



