46 Mr. A. M. Worthington on a Point 
slide within it, so that by gentle pressure against a hard 
plane surface the edges of the convolutions can at any time 
be very accurately adjusted to the same plane. Other forms 
might doubtless be given to the multiplier, but the cylin- 
drical coil is the most compact and requires for its use the 
smallest amount of liquid. The labour of double-threading 
the long strip of beads is considerable, and I have tried to 
avoid it by substituting a strip of asbestos cardboard, which 
would allow the coil to be cleansed by the action of the flame 
as before. But though in other respects satisfactory, the 
asbestos very rapidly gains in weight through the absorption 
of the vapour of many liquids, and cannot therefore be used 
unless wrapped in very thin platinum foil; but when so 
wrapped it is troublesome to coil, and does not allow the same 
ready adjustment of the edges of the coil to one plane. 
Clifton College, Bristol, 
October 16, 1884. 
IV. Note on a Point in the Theory of Pendent Drops. 
By A. M. Worruineton, M.A. * 
[Plate I. figs. 3-6. | 
N a paper on Pendent Drops (Proc. Roy. Soc. no. 214, 
1881) I explained how, from a tracing of the outline of 
a drop pendent from a circular base, the value of the surface- 
tension of the liquid could be deduced with an accuracy that 
compared favourably with that of any other method. 
The most difficult part of the process is the measurement 
at various levels of the inclination of the tangent of the curve 
to the axis; and I find that this difficulty does not disappear, 
as I hoped it might, when a photograph of the magnified 
image of the drop is substituted for a tracing made by hand. 
It is essential to the success of the method to measure this 
inclination at levels where the horizontal sectional area of the 
drop is widely different. Thus in a drop shaped as in fig. 3 
Plate I. it would be desirable to measure the inclination, say, 
at the level AB and again at the level CD. Now at AB, 
where the inclination changes very slowly, its value may be 
very accurately determined ; but at CD the change of incli- 
nation is rapid and its determination difficult. 
Tt has lately occurred to me that the necessity of finding 
the value of the inclination at more than one level may be 
* Communicated by the Physical Society: read November 22, 1884 
(communicated by J. H. Poynting). 
