MR. H. TOMLINSON ON THE COEFFICIENT OF VISCOSITY OF AIR. 
795 
Nap. log. dec. = 
2M>y 
MIC 
X real part of ma 
3.5 1.3.5,7 1 2 .3.5.7.9 
1.8m<x 1.2(8 ma) 2 1.2.3(8ma) 3 "^ 
1 + 
1.3 
1 2 .3.5 
+ : 
1 2 .3 2 .5.7 
( 21 ) 
1.8 ma 1.2(8ma) 2 1.2.3(8m«) 
Instead of the latter part of (21), in which, however, the law of either series is 
manifest, we may use its development according to descending powers of a, which is 
3456 . 60768 1327104 
3 _3_ 24 252 
ma 2 8 ma (8 maf (8 ma) 3 (8 may 1 (8 mdf 
(■ 8ma ) 6 
• • ( 22 ) 
The expression for the correction for the internal air will be got from the above by 
changing the sign of ma and of the whole, or, in other words, by changing the signs 
of the 2nd, 4th, 6th . . . terms in the series in (21) or (22). It will be remembered 
that ma is /(cos 45°+i sin 45°). 
Appendix. 
(Received November 15th, 1886.) 
In the previous experiments the main loss of energy arising from the friction of the 
air may be characterised as being due to the fact that the air is pushed. A small 
portion, however, of the loss is occasioned by the rotation of the cylinders or spheres 
about their own axes, and in this case the air may be said to be dragged. Professor 
G. G. Stokes has, in the preceding note, deduced formulae by means of which this 
last portion of the whole loss of energy can be calculated, and it seemed of interest 
to determine whether the coefficient of viscosity of air would prove to be the same as 
before, when the air was entirely dragged. This will occur when only one sphere or 
one cylinder is used, whose axis is made to coincide with the axis of rotation. 
Accordingly I followed out a suggestion of Professor Stokes in the manner detailed 
in the following experiments. 
Experiment VI. 
A paper cylinder was made by wrapping drawing-paper several times round a metal 
cylinder, which had been turned true throughout its whole length, the different layers 
being pasted together. When dry, the paper cylinder was removed from its metal 
core, and its external diameter very carefully gauged by calipers reading to T'oooth of 
an inch at six different places equidistant from each other. It was then gauged at 
the same distances from the ends, but in directions at right angles to the first. The 
following were the two sets of gauges :— 
5 I 2 
