134 M. V. Regnault on the Expansion of Gases. 



wound on the same cylinder; each of these tubes is 1^ metre in 

 length, and their internal section is 6 millims. Between these two 

 tubes is intercalated a silver capillary tube, the internal calibre and 

 length of which are varied. This tube is coiled in a spiral on 

 the same cylinder as the portions of the copper spiral between 

 which it is intercalated, and it is hermetically cemented by means 

 of tin-solder. The water of the calorimeter, and that of the bath 

 (which gives to the air a known temperature before it reaches the 

 worm of the calorimeter), are kept in a perfectly uniform state 

 of agitation. The temperatures are indicated by thermometers, 

 each Centigrade degree of which has twenty divisions, and which 

 have been accurately compared at the same temperatures as those 

 they are exposed to in the experiments. 



When the stopcock of the reservoir with compressed air is 

 opened, the air traverses the worm of the bath without sensible 

 change of pressure, but assuming the temperature of the water, 

 and passes without any change of pressure into the first part of 

 the copper worm of the calorimeter. Expansion commences at 

 the entrance into the narrow silver worm ; and on emerging from 

 this capillary tube the air flows through the second part of the 

 copper worm, where it resumes the pressure of the atmosphere, 

 and emerges after having assumed exactly the temperature of 

 the water of the calorimeter. 



In four series of experiments the length of the capillary 

 tube varied from 0*09 metre to 1*79 metre; the quantities of gas 

 which emerged in a minute varied from 2*2 grms. to 13'5 grms., 

 while the values of y remained almost exactly the same. Yet, 

 from the results of the fourth series, it must be admitted that 

 they increase with the velocity of the outflow — that is to say, in- 

 versely as the length of the tube. This fact may be attributed 

 to heat disengaged by the friction of the gas along the sides; 

 but it is far more probable that it arises from the fact that the 

 gas retains then a greater velocity on emerging from the calori- 

 meter, and that it thus carries off a greater quantity of heat in 

 the state of vis viva. 



In three new series the lengths of the capillary tube varied 

 from 0*07 metre to 1*16 metre; the quantities of gas which 

 emerged per minute changed from 12 to 46 grms. ; but the 

 values of y only underwent very small alterations : they increase 

 with the velocity of the outflow more regularly than in the group 

 of the first four series. We arrive therefore at the same con- 

 clusion. 



In other experiments I suppressed the two pieces of wider 

 copper tube between which the capillary silver tube was inter- 

 calated, so that the air emerged directly from the capillary tube 

 into the atmosphere. 



