8 4 
Dr. Young’s Essay 
second in that of the common surface of the solid and fluid, 
and the third in that of the exposed surface of the solid. Now, 
supposing the angle of the fluid to be obtuse, the whole super- 
ficial cohesion of the fluid being represented by the radius, the 
part which acts in the direction of the surface of the solid will 
be proportional to the cosine of the inclination ; and this force, 
added to the force of the solid, will be equal to the force of the 
common surface of the solid and fluid, or to the differences of 
their forces ; consequently, the cosine added to twice the force 
of the solid, will be equal to the whole force of the fluid, or to 
the radius : hence the force of the solid is represented by half 
the difference between the cosine and the radius, or by half the 
versed sine ; or, if the force of the fluid be represented by the 
diameter, the whole versed sine will indicate the force of 
the solid. And the same result follows when the angle of the 
fluid is acute. Hence we may infer, that if the solid have half 
the attractive force of the fluid, the surfaces will be perpendi- 
cular ; and this seems in itself reasonable, since two rectangular 
edges of the solid are equally near to the angular particles 
with one of the fluid, and we may expect a fluid to rise and 
adhere to the surface of every solid more than half as attractive 
as itself ; a conclusion which Clairaut has already inferred, in 
a different manner, from principles which he has but cursorily 
investigated, in his treatise on the figure of the earth. 
The versed sine varies as the square of the sine of half the 
angle : the force must therefore be as the square of the height 
to which the fluid may be elevated in contact with a horizontal 
surface, or nearly as the square of the number of grains ex- 
pressing the apparent cohesion. Thus, according to the expe- 
riments of Morveau, on the suppositions already premised, 
