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formed : indeed it is sometimes formed and sometimes not 
under apparently similar conditions. No doubt the proxi- 
mate cause is that the drop, at the instant of separation is 
not spherical : the persistent or retentive cohesion which 
brings it almost immediately to its normal shape, does not 
allow time for its more excentric parts to collect to the main 
mass ; they are therefore, by the motion of the main drop, 
flung ofl' and projected upwards. 
The same phenomenon is seen much more distinctly when 
water drops at this rate {gt.—tj”) through benzol or turpen- 
tol. In these cases the persistent cohesion of the liquid me- 
dium comes also into play. 
But the most striking example of supplementary drops is 
seen when glycerine forms the medium through Avliich mer- 
cury drops. In this case when gt=5” there are always two 
supplementary drops of mercury formed. It is impossible to 
dertermine whether they both have their origin at the same 
moment and from the main drop. The probability however 
is that they have not : but that one is first separated from the 
main drop and the second from the first. For there is always 
a great disparity between the sizes of the two supplementary 
drops : whereas, if they were both formed at the same time 
and for the same reason we should not expect such a con- 
sistent difference. The drops soon separate in falling, in con- 
sequence of the difference of their surfaces. The relative sizes 
of the main and supplementary drops in the ease of mercury 
falling from copper through the glycerine were determined as 
follows. A number of porcelain cups Fig. IX. were arranged 
at the bottom of a shallow dish full of glycerine. When thy 
rate of dropping was uniform at gt= 4”, the dish was shifted 
horizontally, so that every drop with its two supplements was 
caught in a separate cup. The globules of mercury in each 
cup were removed by a little copper-foil ladle. Ten of each 
kind were collected. After washing and drying they were 
" f'iobed with the fo] lowioi:' result : 
