28 ESSAYS anp OBSERVATIONS 
18. Ir that furface were perfectly fmooth, 
the under furface of the drop would be fo 
hikeways; and would therefore ihow an_ 
image 
5 
Jar to AB, the common tanzent of thefe curves, which 
will be the continuation of the general furface of the wa- 
ter. The forces with which any two particles, E and F, 
are prefled by the water in the dire@ions EG, *H perpea- 
cicular to KB, are known to be as K% and KH, and the 
repulfive powers which balance them muft be in the fame 
proportion. ff therefore the relation between the ordi- 
na‘e and abfcifs in the curve DM could be any way found 
by experiment, the law of the repulfive power might be 
determined, upon fuppofition that the particles are influy 
enced by no force but the repulfive power of the line KB- 
and the gravity of the fuperincumbent fluid ; but their 
mutual attraction, which tends to leffen their lateral cen- 
dency, muft be likeways taken into the account in order. 
to an exaét determination. 
Before I Jeave this fubjed of attragtion and repulfion, 
J beg leave to propofe to the Society, the f{pontaneous 
motions of light bodies on the furtaces of fluids, as_a 
thing worthy of being inquired into 3 for, though it be 
manifeft in general that they depend upon the different 
figures of the furface, it is far from being an ealy matter 
to explain the particular cafes by mechanical or hydrofta- 
tical laws. The following account of the phenomena may 
be nfeful towards fuch anenquiry. Ca/e1. Suppofe a 
fluid which is attracted to the fide of its containing veflel, 
and confequently ts eleyated, at the fides, into a concave 
furface: 
