30 ESSAYS anp OBSERVATIONS 
the under furface becomes rough like- 
ways; and fo, by refleAling the light co- 
pioufly in different directions, affumes 
the 
an accelerated motion, Cafe 4. If, ina fluid which is . 
formed into a convex furface at the fides, a repelling 
body be immerfed; as foon as its depreflion begins to 
unite with the lateral depreffion of the fluid, it will move 
towards the fide with an accelerated motion. In thefe 
two laft cafes, the fame obfervation holds as with refpect 
to the frft and fecond, viz. that the whole fluid will 
move with correfpondent motions by the force of reaétion, 
if the repelling body. be held fait. Cafe 5. If two bo 
dies be immerfed in a fluid, which each of them attracts; 
as foon as their elevations begin to join, they will ru(h 
towards one another with equal forces and accelerated 
motions, and continue to adhere together. Cafe 6, If 
two bodies be immerfed in a fluid which they repel; as 
foon as the two depreffions that {urround them begin to 
interfere, they will likeways rufh together with an acce 
lerated motion. Cafe 7. It two bodies be immerfed ina 
fluid, the one of which attracts and the other repels it 5 
as foon as the depreffion furrounding the one begins to 
join with the elevation of the other, they will mutually 
fly from each other. Lafily, if a body be immerfed in a 
fluid wh-ch it attracts in one part and repels in another, 
it will approach to or recede from other bodies and parts 
of the fluid, differently according to its tituation, by the 
rules above laid down. 
The different figures afcribed to the furface of the wa 
ter in thefe feveral cafes are plainly difcernible by the 
fight; 
