ME. CLEEK MAXWELL OX THE DYXAMICAL THEOEY OF GASES. 
85 
These numbers are to be regarded as doubtful, as we have supposed air to be a simple 
gas in our calculations, and we do not know the value of k between oxygen and nitrogen. 
It is also doubtful whether our method of calculation applies to experiments such as the 
earlier observations of Mr. Graham. 
I have also examined the transpiration-times determined by Graham for mixtures of 
hydrogen and carbonic acid, and hydrogen and air, assuming a value of k roughly, to 
satisfy the experimental results about the middle of the scale. It will be seen that the 
calculated numbers for hydrogen and carbonic acid exhibit the peculiarity observed in 
the experiments, that a small addition of hydrogen increases the transpiration-time of 
carbonic acid, and that in both series the times of mixtures depend more on the slower 
than on the quicker gas. 
The assumed values of k in these calculations were — 
For hydrogen and carbonic acid k=12‘5 XlO 10 , 
For hydrogen and air . . . . #=18-8 X 10 10 ; 
and the results of observation and calculation are, for the times of transpiration of 
mixtures of — 
Hydrogen and Carbonic acid. 
Observed. 
I Calculated. 
Hydrogen and Air. 
Observed. 
Calculated. 
100 
0 
•4321 
•4375 
100 
0 
•4434 
•4375 
97*5 
2-5 
•4714 
•4750 
95 
5 
•5282 
•5300 
95 
5 
•5157 
•5089 
90 
1-0 
•5880 
•6028 
9° 
10 
•5722 
•5678 
75 
25 
•7488 
•7438 
75 
25 
•6786 
•6822 
50 
50 
•8179 
•8488 
50 
50 
•7339 
•7652 
25 
75 
•8790 
•8946 
25 
75 
•7535 
•7468 
10 
90 
•8880 
•8983 
10 
90 
•7521 
•7361 
5 
95 
•8960 
•8996 
0 
100 
•7470 
■7272 
0 
100 
•9000 
■9010 
The numbers given are the ratios of the transpiration-times of ''mixtures to that of 
oxygen as determined by Mr. Graham, compared with those given by the equation (140) 
deduced from our theory. 
Conduction of Heat in a Single Medium (y). 
The rate of conduction depends on the value of the quantity 
where § 3 , and f£ 2 denote the mean values of those functions of |, £ for all the 
molecules in a given element of volume. 
As the expressions for the variations of this quantity are somewhat complicated in a 
mixture of media, and as the experimental investigation of the conduction of heat in 
gases is attended with great difficulty, I shall confine myself here to the discussion of a 
single medium. 
Putting 
Q=M(«i.+ { w 2 -f v 1 -\-w 2 + 2 2wj+ 2w£ + jS(| 2 + + £ 2 ) } , . . . (142) 
