ADVERTISEMENT. 
THE following Memoir was written on one of two 
Subjects, propofed by the Academy, agreeably to the 
Dire&tion of a Perfon unknown, who gave 1oo/. to be 
difpofed of by the Academy in Prizes of 50/. to the 
beft Efflay on each Subje&. One of the Prizes was 
adjudged to the following Effay, which was ordered to 
be publifhed in the TranfaGtions of the Academy, by 
a Vote of Council July oth, 1792. 
