the other two and because it will be convenient to consider 
together those cases which are capable of inversion. 
As we are considering the physical aspect of the question, 
we will onlv discuss those cases where no chemical action takes 
place between the terms and where either no solution takes 
place or where it is so small as to be negligible, or of such Ji 
kind as to admit of experimental elimination. This limitation 
of course excludes a vast number of combinations, but it must 
be made in order to study the purely physical and definite 
influences which determine the size of a drop. 
I.—SLG, From a Solid , a Liquid Drops through a Gas. 
The variable factors are : 
1. The self attraction and cohesion of the liquid. 
A. dependent upon its purely chemical constitution. 
13. dependent upon the proportion between its hetero- 
geneous parts. 
C. dependent on temperature. 
2. The adhesion between the solid and the liquid. 
A. as in 1. 
13. as in 1. 
I 
C. as in 1. 
D. dependent upon the shape of the solid. 
3. The adhesion of the gas to the solid. 
A. 13. C. as in 1. 
E. dependent on atmospheric pressure. 
4. Adliesien of the gas to the liquid. 
A. B. C. E. as in 3. 
One of these factors, namely, Temperature, though varying 
in different cases, may be supposed, in the same case to be 
the same for the different kinds of matter present. 
Another factor in the same predicament is flic locally con- 
stant gravitation at the place where the dropping takes place. 
Lastly, a condition of great influence is the extent ot the 
time interval between the successive drops. This interval we 
shall call for brevity the growth-time of the drop, and repre- 
sent by gt. 
