104 Prof. Magnus on the Propagation of Heat in Gases. 



ving the mirror with which the lamp was provided, and placing 

 the lamp itself at greater distances. For it appeared not impro- 

 bable that the values of the galvanometer corresponding to the 

 deflections, which for greater deflections are not capable of such 

 exact determination as for smaller ones, might have caused the 

 great difference in the radiation through rarefied air, and through 

 air at the normal pressure. With the blackened tube it was 

 not possible to dispense with the mirror ; and hence, in order to 

 produce a smaller deflection, the resistance of the wire connected 

 with the galvanometer was increased. In this way the following 

 values were obtained : — 



Blackened tube. 



Unblackened tube. 



No. 



Position 

 of equi- 

 librium 

 of the 

 needle. 



Mean. 



Ob- 



served 

 deflec- 

 tion. 



Differ- 

 ence. 



No. 



Position 

 of equi- 

 librium 

 of the 

 needle. 



Mean. 



Ob- 

 served 

 deflec- 

 tion. 



Differ- 

 ence. 



Atmospheric air under 1 atm. pressure. 



1 



00 

 



+0-5 

 +0-5 

 +0-5 



o 



00 



+0-25 



+05 



+0-5 



110 



11-25 



11-5 



115 



110 



110 

 11-0 



no 



I 



+20 + 1/0 



28-25 

 2875 

 28-50 

 28-50 



26-50 

 2675 

 2675 

 2675 



Mean 11-0 



Corresponding to ... 11*0 



Mean 

 Corres 





2670 



ponding to ... 



36-3 



Under 4 millims. pressure. 



Under 9 millims. pressure. 



la 



+05 



+05 

 +05 

 +0-5 

 +05 



+0-5 

 +05 

 +0-5 

 +0-5 



120 

 1175 

 120 

 120 



11-5 

 11-25 

 11-5 

 11-5 



la 



o-o 



0-0 

 -0-2 

 -02 

 -0 2 



00 

 -01 

 -0-2 

 -02 



290 

 290 

 290 

 290 



290 

 291 

 29-2 

 29-2 



Mean 115 



Corresponding to ... 115 

 I: Ia = 110: 11-5 = 100:103-8 



Mean 29-1 



Corresponding to ... 41*2 

 I:Ifl=36-3:41-2 = 100:113-5 



Unblackened tube. 



Atmospheric air under 1 atm. pres. 



Atmospheric air under G millims. pres. 



II 



-10 

 -10 

 -10 

 -10 



-10 



-10 

 -10 

 -10 

 -10 



13-0 14-0 

 130 1 140 

 130 14-0 

 130 | 140 



Ila 



-1-5 

 -15 

 -1-5 

 -1-5 

 -1-5 



o 



-1-5 



-1-5 

 -1-5 

 -15 



o 



147 

 147 

 14-5 



150 



16-2 

 16-2 

 160 

 16-5 



Mean 





140 



140 



TU„™ 





16-2 

 16-4 

 171 





Corres 



ponding to ... 



II: 



Corres 

 IIa=l^ 



ponding to ... 

 i: 16 4 = 100:1 



