: 
on the Planet Mars. ~ B48 
£983, Sept. 9. Pofition of the fuppofed fouth pole of Mars 
65°12’ fouth following; 7 feet reflector ; power 460. 
Sept. 22. Pofition of the fame 52°9' f. following; 460. 
Sept. 25. 13h. 30’. Pofition of the fouth polar fpot 
56° Us very accurately taken, by bifeGting the 
difle of Mars through the bright f{pot, and fuppofing 
the planet now near enough the oppofition to induce 
no material error. Hitherto I have taken it through 
a fuppofed center by endeavouring to allow a little 
for what I thought the deficiency in the difks; but 
not to-night. 
‘OG. 4. 8h. 46’. Pofition of the {pot 51° 21’; Mars 
too low and hazy to depend much on the meafure 
with fo high a power as 460. 
O& 5. The motion of the polar {pot being now w ftrongly 
fufpe&ted, or rather already known, I took the fol- 
lowing meafures, by way of difcovering its quantity. 
11h. 50’. Pofition very exactly taken 50° 6’ f. fol- 
bee 
14h. 0’. Pofition of the ae 49° 45’ 
Om 7. 8h. 20’. Pofition 55°12’. In order to fee how 
far this meafure might be trufted to, I fet 49° 36’ in 
the micrometer, which was evidently too {mall; 
next I took 51° 36’, which was alfo too {malls after 
this, I took a new meafure, and found 55° 24’, 
which appeared to me very exat. 10h. 5’. The 
pofition now was 53°. 11h. so’. It meafured 52° £2'. 
As there is nothing te diftingith the center, itis ex- 
tremely difficult to pleafe one’s felf in bringing the 
{pot into a line with it. 
Vou. LXXIV, Ll 1783, 
