778 
MR. H. TOMLINSON ON THE COEFFICIENT OF VISCOSITY OF AIR, 
From these and the previous data we can, by means of equation (2), get 
k' = 1-6122] 
and hence, by interpolation, we can obtain from the table on page 46 of Professor 
Stokes’s paper 
m = 1-1327. 
Again, substituting this value of m in equation (3), we obtain as the value of /u, 
in C.G.S. units, at the temperature of I2°-02 C, 
•00018294. 
Experiment II. 
Two hollow cylinders, made of drawn brass tubing, and closed at both ends, were 
used instead of the paper cylinders. As measured by a gauge reading to Ttioth of a 
millimetre, the mean diameter of one cylinder was 0"96446 centim., and of the other 
0 "9 62 79 centim. These values were obtained by gauging each cylinder in ten different 
places, equidistant from each other, and in the calculations each cylinder was assumed 
to have a mean diameter of 0"96363 centim. The length of one cylinder was 
60 - 92 centims., and of the other 60"85 centims., whilst the mean of these numbers, i.e., 
60"885 centims., was assumed to be the length of each cylinder. The mass of each 
cylinder was 91 "900 grammes, and when the cylinders were on the bar V Y the moment 
of inertia of the whole vibrator, in centimetre-gramme units, was 36702. The value 
of the vibration-period was 7‘0590 seconds. The temperature of the air was 14°’63 C., 
and the barometric height 29"707 inches. The uncorrected logarithmic decrement due 
to the resistance of the air on the cylinders was "0012338, and the corrected logarithmic 
decrement was '0012546. From these data was deduced a value of p, at the tempera¬ 
ture of 14°'63 Cl, of 
•00017718. 
Experiment III. 
Everything else was arranged in the same manner as in Experiment I., but, instead 
of the annealed copper wire, an annealed silver wire, 97 centims. in length and 
0100863 centim. in diameter, was used. The paper cylinders employed in Experi¬ 
ment I. were used here, and when these cylinders were on the vibration-period was 
3*0198 seconds. The temperature of the air was 11°"69 Cl, and the barometric 
height 30"207 inches. The uncorrected logarithmic decrement due to the resistance of 
the air against the cylinders was "0016871, and the corrected logarithmic decrement 
*0016905. The value of /x at the temperature 11°-69 C. was calculated to be 
*00018143. 
