
THE COHESION OF LIQUIDS. 699 
a graduated scale D. The bore of the plug of the stop-cock was merely a 
narrow slit, instead of the usual round hole, so that the motion of the handle 
made only a slight increase or decrease on the flow. In this way the rate could 
be regulated to a nicety. If 
necessary, pressure could be ap- 
plied through the tube E, while 
the tube F gave the lower part 
of the apparatus free access to 
the atmosphere. The tube from 
which the liquid drops was so 
adjusted that it just held the 
mercury as a column, so that it 
exerted no attractive influence 
upon the liquid. By means of 
this apparatus the dropping of 
liquids may be examined in 
various atmospheres, as by the in- 
troduction of another tube, like 
F, a current of any gas or vapour 
may be passed through the appa- 
ratus. It was found that with 
the above arrangement, if the 
drop fell from a sufficient height 
to be audible, the vibration of 
the apparatus interfered with the 
size of the drops, and when a 
high rate was used, if the drop- == 
pings were not audible, the eye as 
was quite incapable of counting Fig. 1 
correctly. The dotted curve in 
the plate shows the variation in the weight of the drop, owing to the vibration of 
the apparatus when the dropping of the mercury was audible. The explanation 
of this is, that when the drop is nearly normal, or about to break, should the swing 
be upwards it gains time, and consequently the drop is larger than it should be, 
and when the swing is downwards it breaks off the drop before it has attained 
its normal size. It was thus seen that for high rates of dropping an apparatus 
would be required in which the drop might fall outside the apparatus, so as 
to be audible without shaking, or that it might be counted automatically. The 
latter method was ultimately adopted, and the apparatus, of which the following 
is a sketch, shows the method used. It must be remembered, however, that 
this apparatus could only be used for ordinary temperatures, as the drop would 































































































