250 °N" * H1 TRANSMISSION Of WfcAl*. 



objection. But even the firjfr, that caloric does not radial? 



through a tranfparent fluid, has been fufficiently proved by 



the experiments of C. Rumford. I fhall add one of a fimilar 



kind made with the particular apparatus ufed in the preceding 



Experiments of experiments, which appears to me fufficientlv decifive. The 

 radiation; with . . ; ri ,. , • , ., 



remarks. thermometer m the ice cylinder was covered with 01! one' 



quarter of an inch, and the cup was fufpended 6ver it in fuch 

 a manner that the bottom of it, though near to the furface of 

 the oil, did not touch it. Boiling water was poured in> the 

 thermometer rofe fcarcely one degree in five minutes, and did 

 not rife more in any longer time. It has been fhewn that 

 when the thermometer was covered with one quarter of an 

 inch of oil, and the cup filled with warm water, was fufpended 

 fo as to touch the furface, it rofe in feveh minutes 5§ degrees. 

 Had this rife been owing to the communication of caloric by 

 radiation, the variation in the experiment which has juft been 

 related, could not have produced any change in the refult. 

 The Communication of temperature by the condu&ing poner of 

 the fluid, muft be facilitated by the contact of the fluid with 

 the heated folid, but the communication of it by radiation re- 

 quired no fuch aid, nor could it be promoted by it. The 

 mere circumftance of the heated folid not touching the fluid, 

 could make no difference with refpect to the one, but muft 

 make the molt effential difference with regard to the ether, 

 and the experiment clearly proves, that even through tranf- 

 parent fluids caloric does not radiate. The flight rife of tem- 

 perature that took place, is owing to the caloric pafling partly 

 by radiation, and partly by communication by the medium of 

 the air to the furjace of the fluid, and from that it is conveyed 

 by the conducting power of the fluid to the thermometer. The 

 proof of this is, that even with mercury, a flight rife of tem- 

 perature was indicated when the experiment was performed 

 in the fame maanner. When the cup with hot water was fuf* 

 pended over the mercury covering the bulb one quarter of an 

 inch, but not touching it, the thermometer rofe one degree. 

 Concluding re- jt mav therefore from the whole of thefe experiments be 

 concluded, that the obferved rife of temperature was owing 

 to the fluid conducting Jhe caloric, fince no other caufe can 

 fairly be affigned. I have not fubjetted any other fluid to 

 experiment, becaufe it was difficult to find any of a nature 

 fufficiently different, which the ice would have been capable 



of 



marks. 



