825 Prof. J. J. Thomson, On the Effect of Pressure and [Jan. 28, 
the apparatus is then screwed on to L’GF’H, the end H dipping 
under the mercury, then by screwing in the screw a pressure 
sufficient to liquefy the CO, can easily be obtained; the piece 
of paper placed at H being pierced by the mercury when the 
pressure is increased. Two electrodes are fused in the tube and 
are placed in multiple arc with two brass balls U and V of very 
large radius, the distance between which can be adjusted by 
means of a screw. U and V are connected with the poles of an 
induction coil. To estimate the electric strength of the CO, the 
distance between the balls U and V is altered until as many 
sparks pass through the CO, as through the air, when the 
distance between the balls U and V is taken as a measure of 
the electric strength of the carbonic acid. This method, though 
not free from objection, is very convenient, and if care be taken 
to keep the air surrounding the balls free from dust and carefully 
to prevent by continued polishing the surface of the balls from 
getting roughened by the sparking gives consistent results. 
Experiments were made at different pressures and it was 
found that the electric strength of the CO, continually increased 
with the pressure and that this increase goes on past the point 
of liquefaction, that is, that the strength of the liquid CO, is 
greater than that of the gaseous CO, just before liquefaction. 
It was found impossible to determine more than a lower limit 
