196 ROYAL SOCIETY OF CANADA 



I. — Calorimeter scale divisions due to the heat from the air = (6.612 - 5.0071) 



= 1.6049. From Fig. 7 and its corresponding readings the number 



of calories per minute due to the heat imparted by the air = 1.20327. 



II.— Average fall of pressure = .3399^gauge divisions per minute, = 17.09 mm. 



mercurj' per minute and consequently the average rate of flow = 

 .20355 grams per minute. 

 Combining I and II the value .2697 was obtained for the specific heat at 

 constant pi-essure. 



F. Discussion. 



In the published account of the experiments in which he determined 

 this constant. Eegnault gives the results of eight-four determinations. 

 These var_y from .22 to .24 the average value being .2375. The result 

 found from the observations given above, while somewhat higher than 

 those found by Kegnault is still sufficiently near to his values to demon- 

 strate the usefulness of the method. 



(j. Alterations Suggested. 



One or two changes m the arrangement have suggested tnemselves, 

 but owing to lack of time, have not as yet been tried. In the first place 

 the junction of the two tubes at d might be made quite near to the upper 

 end of the test tube of the calorimeter, and the thermo junction moved 

 up to correspond. This would not alter " x " as used in the above dis- 

 cussion, but would make a much greater value of " t " and a correspond- 

 ingly smaller value of "x^" since the heat given up by the air betveeen the 

 present position of d and that suggested is at present included in "Xq." 

 Again, an ebonite connection in the tube d would lessen the conduction 

 from the steam jacket, ebonite being a poor conductor of heat. This 

 would lesson the values of "x" and "x^" by equal amounts. Both these 

 changes would lessen the percentage error in the final result. 



H. Advantages of the Method. 



Some advantages of this method over that used by Eegnault may 

 be enumerated. 



(1) JBy this method the calorimetry is more perfect than in the 

 experiments of Eegnault, since the calorimeter (a) is very much more 

 sensitive and (b) it requires no correction for radiation on account of 

 belonging to the constant temperature type. 



(2) Heat communicated by all sources other than the gas itself, for 

 example, by conduction from the steam jacket down the tube, d. and 

 from the air of the room dowù a and h, is accounted for by a single 

 direct observation. 



