1 8 1 u .] Specific Heat of I he different Gases. 2 1 9 



is the same tube that is represented by G I in the horizontal 

 section of the apparatus, fig. 5. 



M M, N N, are two oval plates, pierced in their centre by a 

 circular opening, which receives the vapour tube, to which they 

 are firmly fixed. At each of their extremities is a hole, suffi- 

 ciently large to give passage to the rods, b b, b' b\ fixed to the 

 calorimeter, and represented in fig. 6. 



It is easy to see that when the extremity of the vapour tube is 

 presented "to the calorimeter, and the metallic rods are made to 

 pass through corresponding openings in the wooden disks, M M, 

 N N, the opening, I I, of the gas tube will be exactly opposite 

 to the opening, d d, of the serpentine. If we interpose between 

 the two openings a tube of glass of the requisite size, and such 

 that its extremities, ground with care, press against the disks of 

 leather which cover the flat faces, J'f, L L; and if, by means of 

 the nuts, C, C\ we force the extremities of the vapour tube to ap- 

 proach as near as possible to the calorimeter, then the tube of glass 

 firmly fixed between' the two disks of leather will establish a com- 

 munication between the gas tube and the calorimeter, and will 

 prevent all gas from escaping in any other direction. 



In describing our apparatus we have said that the calorimeter 

 was in a different room from that of the rest of the apparatus, 

 and that the communication took place by means of a hole made 

 in the door (fig. 5). As a part of the vapour tube was in the 

 same room with the calorimeter, it was screened from the effect 

 of radiation by covering the hot tube with a box of tin plate, 

 properly disposed to allow no radiant heat to pass, and that the 

 air which surrounded this tube should have no communication 

 with that which surrounded the calorimeter. 



Notwithstanding all these precautions wc could not prevent 

 the calorimeter from being a little heated by the vapour tube by 

 immediate communication. We endeavoured to determine to 

 how much that cause of heat amounted. We have ascertained 

 that when it acted alone it amounted to 3'1 C (54-° Fahrenheit); 

 and we think we may, without sensible error, reckon it at 2*5° 

 : 1 ' Fahrenheit) when the calorimeter was heated likewise by 

 the current of hot gas.* 



The preceding details, perhaps, will be thought rather long; 



but we considered it improper to omit them, because they will 



reader to appreciate the accuracy of our results. We 



hope that the experiments which we shall next describe will 



merit the confidence of philosopher's and chemists. 



{To be cuntinueil.) 



» See note 1 at the end of this paper, 



