on the Planet Mars. 263 
diately, but thought the flattening almoft as much 
as that of Jupiter. Mr. Avsert alfo faw it very 
plainly, fo as to entertain no manner of doubt about 
the appearance. 
As we cannot take too many opportunities of confirming 
_ our own obfervations by the eyes of other obfervers, I efteemed 
it a very fortunate circumftance to have the honour of a vifit 
from thefe gentlemen at fo particular a time, Mars being this 
day within 37 hours of the oppofition, and yefterday when 
Mr. Witson faw it, within about two days and a half. 
1783, Sept. 30. roh. 52’. The difference'in the diameters of 
Mars is very evident and confiderable. 
Meafure of the equatorial diameter 22” 9!” with 278. 
Second meafure - “5 22/031" full large. 
‘Polar diameter very exat 0 =. 25’, 26/7", 
O&. 1. roh. 50’. I took meafures of the diameters of Mars 
with my 20-feet reflector. The equatorial meafured 
103 parts of the micrometer; the polar 93. The 
value of the divifions in feconds and thirds not being 
well determined, on account of fome late. change in 
the focal length of the feveral 20-feet object metals f 
ufe, we have only from thefe meafures the propor- 
tion of the diameters as 103 to 98. 
r3h. 15’. Every circumftance being favourable, I took 
the following meafures of the diameters of Mars 
with my 7 feet reflector, and a diftinét power of 
625. 
Equatorial diameter . 22’’ 12’’’ narrow meafure.. 
22” 46’ rather full. 
221 3517" exact, 
Polar 
