J72 0N THE PASSAGE OF HEAT THROUGH FLUIDS. 



and no precau- Every precaution that can be taken to obviate this fourco 

 cfe^taof the °f error > defeats the purpofe of the experiment itfelf, fines 

 ■experiment. fuch precautions tend equally to leffen the effect which would 

 refult from a conducting power in the fluid fuppofing it to pol- 

 fefs it, and it mutt therefore remain uncertain to what the di- 

 minished effect which takes place where they are employed, 

 is to be attributed. 

 Other remarks. If for example, the bulb of the thermometer be placed at a 

 great diftance from the matter communicating caloric, it will 

 be a longer time before the thermometer begin to rife, and it 

 will alfo not rife to fo great a degree. But which ever opinion 

 be adopted, whether that the fluid directly conduces caloric, or 

 that caloric is communicated only by the veffel, this ought to 

 be the cafe, fince the circumftances neeeffary for its tranfmif* 

 lion in either way are rendered more unfavourable. 



In like manner when a wider veffel is employed to contain 

 the fluid, the rife of temperature muft be lefs than when a 

 narrow one is ufed, becaufe in this cafe alfo there muff be a 

 larger portion of interpofed fluid to be heated. 



Or when a large portion of fluid is placed above the bulb of 

 the thermometer, and in contact with the fubftance communi- 

 cating the caloric, as with the ball in the preceding experi- 

 ments, the fame diminution of effect mutt take place, becaufe 

 the caloric given out by the ball being abforbed by a larger 

 quantity of fluid, the temperature of that fluid muff be lefs 

 increafed, and it muff have lefs effect either in heating the 

 fides of the veffel, or the thermometer. 

 General cbfer- It appears therefore that in all experiments of this kind, a 

 vationor refult. fource of fallacy rauft be p re lent : the effects of this will be 

 more or lefs considerable according to the circumftances of the 

 experiment, but they cannot be intirely obviated, nor their 

 extent appreciated, fo as to admit of a certain conclufion 

 being drawn. 

 H Gory of the It may not be improper to remark, that the preceding ex- 

 experiments, periments were made laft winter, were ftated in my courfe of 

 lectures, and a concife account of them publifhed in my Ele- 

 ments of Chemiftry. I have now ftated them partly to ihew the 

 infurficiency of experiments of this kind, either to eftablifli or 

 controvert Count Rumford's opinion, but principally as an 

 introduction to thofe I have further to relate, and which ap- 

 pear to me to be free from the fource of error I have ftated. 



This 



