202 Proceedings of Societies. [February, 
Anemometer,” by Captain William Watson, F.U.S. ; “ Meteoro- 
logy of Bangkok, Siam,” by J. Campbell, Staff- Surgeon, R.N.; 
“ Results of Meteorological Observations taken at Calvenia, 
South Africa,” by Kaufmann J. Marks, F.U.S. 
Physical Society, January 15. — Prof. G. C. Foster, Vice- 
President, in the chair. 
Dr. Erck exhibited a constant bichromate of potash battery. 
It consists of a narrow lead trough, 12 ins. long by 
3 ins. wide and 1 in. deep, lined along both sides with the carbon 
plates. The zinc plate, 10 ins. long, is immersed in the solution 
to the depth of an inch midway between the two carbons. A 
continual circulation of the bichromate solution is kept up by 
allowing fresh solution to drop into the cell at one end, and the 
exhausted solution to drop away by a tap at the other end. As 
the space between the two carbons is only about half an inch 
wide, there is merely a thin layer of solution between the posi- 
tive and negative poles. The internal resistance of the cell is 
therefore very low when short circuited, only about £ ohm. To 
obtain the maximum current, about 8 ozs. of solution per hour 
should be supplied. 
Dr. Guthrie, F.R.S., described some of the results he had 
obtained from experiments on the vibration of metal rods or 
lathes fixed in a vice at one end and free to vibrate at the other. 
The experiments were carried on by dusting sand on the rod 
and observing the nodal lines formed by it when the rod was 
vibrated so as to give out notes determined by a monochord. Dr. 
Guthrie’s results showed that the two final segments at the free 
end are equal in length to the inner segment at the fixed end. It 
appears from these experiments that if a free lathe, vibrating 
with a node in the middle but having an even number of seg- 
ments, be clamped at where there is a node we alter its condi- 
tions of vibration. When the lathe is half free the end segment 
breaks up into two parts together equal to the segment at the 
fixed end. In the case of torsional vibration of the lathe the 
position of the longitudinal nodal lines depended to some extent 
on the clamping of the lathe in the vice. 
Prof. Foster pointed out that in a natural node the direction 
of the tangent is varying, whereas in an artificial node it is 
always horizontal. 
Prof. Unwin explained that the sand accumulated at nodes 
because the particles when thrown off the lathe make certain 
horizontal excursions, which tend to move them nearer the points 
of repose of the lathe. 
