[ *7 ] 
In which m : I , as the greater axis of the generating 
ellipfe is to the leffer. A is a c ircular arc, to the 
radius i, whofe tangent is m z — i, or its reciprocal, 
if i cr* i* And l is the natural logarithm of 
S * 7 
jr* S being the fine of the] arc, whofe co-line is ~ 
m 
x i, and V the verfed fine of the fame arc. 
Not e, Th e two firft theorems, by fubflituting t 
for \/w 2 — i, coincide with thofe of Mr. Maclaurin 
for the oblate fpheroid, in his differtation on the 
tides. 
III. A Letter from the Rev . Mr. George 
Coftard, Fellow of Wadham-College, Ox- 
ford, to Dr. Bevis, concer?iinv the ITeur of 
the Eclipfe foretold by Thales. 
Dear Sir, 
Read Jan. 25, THANK you greatly for the ufe of 
X the Peterfburg Adts, while in Lon- 
don, where Bayer fuppofeth the eclipfe foretold by 
Thales to the Ionians fell out the year before Chrift 
6 03. Since my return home, upon looking over 
fome papers, that I had formerly drawn up on that 
fubjedt, I find, that I had determined it to have been 
the very fame year. I will not trouble you with the 
chronological arguments, on which I founded that 
determination ; and therefore fhall only tranfcribe fo 
much of thofe papers as relates to calculation. 
C Riccioli 
