14 PHENOMENON. 
but flightly acquainted with the principles of hydroftatics 
gc. are apt to fancy immediately, that they underftand it, 
and readily attempt to explain it: but their explanations 
have been defficient, and, to me, not very intelligible. 
Others more deeply {killed in thofe principles, feem to 
wonder at it, and promife to confider it. And Y think, 
adds the Door, it is worth confidering. For a new ap- 
pearance, if it cannot be explained by our old principles, 
may afford us new ones, of ufe, perhap in explaining 
fome other obfcure parts of natural knowledge.” 
When I read this account I formed in my own mind a 
folution of the phenomenon which (perhaps from the 
caufe mentioned above) fatisfied myfelf, and have not 
fince confidered the fubjeQ, nor feen any thing written 
upon it, till the other day, when looking over the 2d Vol. 
of the Mancheffer Society’s Memoirs, 1 found the matter 
mentioned there, and two different folutions attempted ; 
one by Dr. Thomas Percival, of Manchefter, and the o- 
ther by Dr. Wall of Oxford. Dr. Percival fuppofes “ that 
the fact in queltion may arife from a repulfive power, fub- 
fifting between the particles of oil and water, and depend- 
ing poflibly upon the vibrations of that fubtile ether, which 
Sir Ifaac Newton fuppofes to pervade all bodies. For when 
this ether is excited into motion, by percuffion or agitati- 
on, its elaftic force is augmented, becaufe it becomes den- 
fer in the pulfes of its vibrations, than ina quiefcent ftate.” 
Dr. Wall thinks * that the commotion, which the water 
undergoes while the oil remains tranquil, depends upon 
the different fpecific gravity of the two fluids (whereby 
they receive the force of the impulfe in unequal proporti- 
ons) and upon the difpofition of the oil, from its. fuperior 
levity, to preferve its place, upon the top of the water, 
whatever agitation the water beneath may be fubjected to.” 
That is, as { underftand it, the water, being fpeci- 
fically heavier than the oil, will, from the action of a giv 
en 
