1881.] On the Viscosity of Gases at High Exhaustions. 451 



oxygen, however, the increase is too great to be entirely attributable 

 to this cause. 



Oxygen has more viscosity than any gas yet examined. The 

 viscosity of air at 760 millims. being 0*1124, the proportion between 

 that of air and oxygen, according to these results, is 1'1185. 



This proportion of 1'1185 holds good (allowing for experimental 

 errors) up to a pressure of about 20 millims. Between that point and 

 1 millim. variations occur, which have not been traced to any assign- 

 able cause : they seem large to be put down to " experimental errors." 

 The discrepancies disappear again at an exhaustion of about 1 millim., 

 and from that point to the highest hitherto reached the proportion of 

 T1185 is fairly well maintained. 



Viscosity of Nitrogen. 



The proportion between the viscosities of nitrogen and air at a 

 pressure of 760 millims. is, according to these experiments, 0*9715. 



A comparison of the air curves with those given by oxygen and 

 nitrogen gives some interesting results. The composition of the 

 atmosphere is, by bulk, 



Oxygen 20"8 



Nitrogen 79*2 



100-0 



The viscosity of the two gases is almost exactly in the same pro- 

 portion : thus at 760 millims. — 



20-8 vis. + 79-2 vis. N . . 



=vis. air, 



100 



20-8(0-1257) + 79-2(0-1092) _ 

 100 



2-61456 + 8-64072 



100 



0-11255, 



a result closely coinciding with 0-1124, the experimental result for 

 air. Up to an exhaustion of about 30 M the same proportion between 

 the viscosities of air, oxygen, and nitrogen is preserved with but little 

 variation. From that point divergence occurs between the individual 

 curves of the three gases. 



Observations on the spectrum of nitrogen are next given. 



The curve of repulsion exerted by radiation is plotted on the dia- 

 grams. It is much lower than in oxygen or air, and sinks rapidly 

 after the maximum is passed. 



Viscosity of Carbonic Anhydride. 

 The curves of this gas are given in diagrams plotted from the 



