M. Achille Cazin on Internal Work in Gases. 



95 



before definitively joining it. In Series III. the minimum of 

 h— about —107 millims. for an abscissa of 2*2 seconds ; then the 

 curve rises rapidly until the abscissa is 7 seconds, and slowly 

 approaches the abscissse-axis, but still remains below it. This 

 latter fact is owing to the inequality of the temperatures of 

 the two reservoirs ; but it will suffice, in order to solve the ques- 

 tion proposed, to observe the agreement of the individual points 

 and the ratio of the ordinates which have the same abscissse. 

 This ratio is exactly the inverse ratio of the densities of the 

 liquids used. Thus for the minimum the densities give 112 

 millims. of water as equivalent to 60 millims. of sulphuric 

 acid. Now the Table indicates a value of 107; and even in 

 two experiments which I have not given in this Table, since 

 they indicate another kind of influence which will be inquired 

 into presently, I have observed 112 millims. and 113 millims. 

 with values of 6 equal to 0*09 second and 0*08 second. Hence 

 the nature of the liquid has no influence on the phenomenon 

 as a whole, if we regard only the magnitude of the pressures ; 

 it manifests itself only by a slight change of the abscissse. Thus 

 the minimum is reached a little later with water than with sul- 

 phuric acid ; this is due to the fact that water, although more 

 mobile than the acid, undergoes a greater displacement at the 

 instant the valve is opened. 



§ VI. Influence of the form and dimensions of the manometer. 

 In Series IV. (air) the manometer was made of a tube 1 cen- 

 tim. in diameter, and the enlargement was a globe of 6 centims. 

 diameter. In Series V. (air) the tube had a diameter of *5 cen- 

 tim., and the enlargement was a cylinder of 1*5 centim. diame- 

 ter. The manometer contained water, and communicated with 

 the tube H (fig. 2). The apparatus was not identical in the two 

 series ; a metal tube, a a', was adjusted in Series V. to the lower 

 orifice of the tube D, with an object which will be afterwards 

 discussed. But the influence sought being sufficiently characte- 

 rized by the results of these two series, I have not thought it 

 necessary to give other proofs. 



Series IV. (May 1867). 

 Dry air. Glass reservoir B. Manometer with spherical enlarge- 

 ment. 

 p j =3*87 atmospheres, jo 2 =0*54 atmosphere. Temperature 

 between 14° and 16°. 



r 0=os-ii 



\A=4-3 mm 



*=... 



4-6 



9-9 



14 



17 





60 



+4 



-66 



-25 



-10 



-5 









(0= 0-13 

 *U=+39 





4-9 



87 



113 



16 



21 



60 





-58 



-28 



-12 







+5 







f 0=0-14 





4-4 



8-5 



12-2 



16 



20 



60 



+ 10 



-70 



-40 



-20 



-9 



-4 







