1879 *] Proceedings of Societies . 581 
Prof. McLeod then described an eledtric clock used in the 
experiments on tuning forks. A z inc and steel compensating 
pendulum moved by its own gravity ; but at each beat made 
and broke a battery circuit by means of two bent springs, one 
on either side. The current passing through an eledtro-magnet 
detained a bent lever until the pendulum swung to the other 
contadt. By this contrivance time was marked. Prof. McLeod 
found that the platinum contacts frequently stuck together in 
these experiments ; but this defedt had been cured by the use 
of a liquid shunt of dilute sulphuric acid, which destroyed the 
extra current. This remedy had been suggested to him by Lord 
Rayleigh. Prof. McLeod demonstrated the complete success of 
this device, which adts as well as a condenser shunt. He had 
also observed a curious effedt with these liquid shunts, which as 
yet he could not explain. Two shunts, having the same acid in 
both, were employed, one shunting the extra current from four 
Daniell cells and one that from two Daniell cells. The first 
showed evolution of H and O gas, the platinum eledtrodes being 
unaffedted. The second showed no evolution of gas, but one 
platinum plate was dissolved awayand deposited in a black powder 
on the other. He also exhibited a new cell formed of zinc and 
mercury plates, with zinc iodide solution and mercurous chloride 
salt. Red iodide of mercury is formed at the negative eledtrode. 
The E.M.F. is seven-tenths of a Daniell-cell, but the interval 
resistance very low and the cell very constant, while there is no 
local adtion. 
Prof. Guthrie suggested that as the extra current was really a 
succession of sparks the platinum might be carried bodily over 
from one eledtrode to the other. 
Mr. F. H. Varley stated that Mr. F. Higgins had observed a 
similar effedt with carbon eledtrodes in a voltameter, one carbon 
falling away into a fine powder, and due perhaps to the disinte- 
grating adtion of liberated gases. He had also himself seen a 
platinum wire in contadt with a carbon one eaten thin and drawn 
into very fine silky pens, while the carbon was stained blue, 
although the current passing was of low tension. 
Mr. Chandler Roberts suggested that perhaps a hydride of 
platinum was formed in the case mentioned by Prof. McLeod. 
Prof. Guthrie suggested experiments with fluorescent liquid 
shunts in the dark. 
Mr. J. W. Clark then described some experiments on the 
surface tension of sulphurous anhydride sealed in a capillary 
tube within a second tube containing the same substance. He 
found that at low temperatures the level of the liquid is lower in 
the narrow than in the wide tube. As the temperature rises the 
meniscus in the narrow tube descends, till at about 156° F. it is 
level with that of the wider tube, both surfaces being slightly 
concave. About this temperature the surfaces become plane 
then concave, the level in the wide tube becoming higher than 
