408 Frof. E. Wiedemann on the Behaviour of Gases 

 same current, and p the pressure, then the value 



A 



SOpz 



w 



expresses what quantity of heat must be evolved in order to 

 change the band spectrum into a line spectrum in a gas of 

 unit-pressure, in which of course the assumption is made that 

 for a given volume the above quantity of heat is proportional 

 to the pressure. The measurements were made with two dif- 

 ferent tubes, of radii 0*304 and 0'183 milium, and are given in 

 the following tables without exception, and in the order in 

 which thev were made. The length of the portion of tube in 

 the calorimeter was 42 millims.: the water-equivalents of the 

 two calorimeters were 11/84 and 12-08. Some of the num- 

 bers were certainly too small, since at the moment the striking- 

 power of the machine did not rise sufficiently to cause a com- 

 plete disappearance of the band spectrum. These are marked 

 with an asterisk, and are left out in determining the mean. 

 Two different series of observations were made with the 

 first tube, of which one includes the first three observations and 

 the other the last four. 



I. 



p- 



a. 



* 



A. 



5-8 

 2-2 

 09 



0-50 

 0-28 

 0-19 



166 

 184 

 181 



0-0000086* 

 0000116 

 0-0000191 



15-3 

 5-4 

 2-1 

 0-9 



0-745 

 0-50 

 0-28 

 0-21 



100 



96 



160 



233 



0-0000081* 

 0-0000158 

 0-0000139 

 0-0000167 







Mean 



... 0-0000155 



II. 



'£>• 



a. 



, 



A. 



9-4 

 3-6 

 17 

 6-2 

 14-1 



0-52 

 026 

 0-20 

 35 

 0-60 



250 

 200 

 270 

 160 



133 



0-00000369* 

 000000615 

 00000726 

 0-00000587 

 0-00000533 







Mean 



.. 00000565 



Two determinations at pressures 2'2 and 0*7 millims. gave 

 for the tube I, whilst bands were still plainly to be seen, 

 A = 0'0000052 and 0*0000057. 



