PHYSICAL ann LITERARY. 187 
IT is worthy of our notice, that, from fe- 
veral phenomena, aftronomers conclude the 
fatellites to revolve on their axis, in the fame 
time that they revolve around their prima-_ 
ries; by which means the exceeding great 
tides that would be produced in them are 
avoided. Thofe arifing from their various di- 
ftances from the primaries, in their apfides, 
may be fufficient for agitating their waters. 
The tides that would .be produced in our 
moon, from this circumftance alone, ought 
to be confiderably greater than the tides pro- 
duced in our ocean ; and poffibly, by a care- 
ful attention to the limits of thofe black parts 
of the moon which formerly were confider- 
ed as feas, but, becaufe of cavities difcovered 
in them, with better telefcopes, are fufpect- 
ed by many to be only large planes, fome 
‘decifion of this queftion might be obtained. 
Water is of too great importance, in natural 
operations, to fuppofe haftily any planet to 
be deprived of it; tho’ we muft alfo allow 
that the variety of nature is not to be limited 
by our conceptions. 
THEOR. 
