on the Planet Mars. — 273 
The largeft of the two ftars on which the above obferva- 
tions were made cannot exceed the twelfth, and the finalleft the 
thirteeenth or fourteenth magnitude; and I have no reafon to 
fuppofe that they were any otherwife affected by the approach 
of Mars, than what the brightnefs of its fuperior light may 
account for. From other phenomena it appears, however, 
that this planet is not without a confiderable atmofphere ; 
for, befides the permanent {pots on its furface, I have often 
noticed occafional changes of partial bright belts, as in fig.. 1 
and 14.3 and alfo once a darkifh one, ina pretty high lati- 
tude, as in fig. 18. And thefe alterations we can hardly 
afcribe to any other caufe than the variable difpofition of clouds 
and vapours floating in the atmofphere of that planet. 
Refult of the contents of this paper. 
The axis of Mars is inclined to the ecliptic 59° 42°. 
The node of the axis is in 17° 47’ of Pifces, 
The obliquity of the ecliptic on the globe of Mars is 28° 42’. 
The point Aries on the martial ecliptic anfwers to our 19° 28 
of Sagittarius. 
The figure of Mars is that of an pale {pheroid, whofe equa- 
_ torial diameter is to the polar one as 1355 to 1272, or as 
16 to 15 nearly. 
The equatorial diameter of Mars, reduced to the mean diftance 
of the earth from the fun, is 9/” 8”. 
And that planet has a confiderable but moderate atmofphere, 
fo that its inhabitants probably enjoy a fituation in a 
refpects fimilar to ours. 
© Datchet, Dec. 1, 1783.0 sy HERSCHEL. 
Vii. LXXIV. Oo 
