242. Mr. HErscHE.’s Ob/ervations 
revolved about’ the poles of Mars. The divifion of the circles: 4 
marked 360 is where a fpot pafles that meridiah of the planet — 
which is turned towards theearth, and where, confequently, it — 
appears to us in its greateft luftre. The motion of the fpot is ac- 
cording to the numbers 30, 60, 92, and fo on to 360. In caleu-- 
lating the daily places of the {pots I have ufed the fidereal period. 
_ of 24h. 39’ 21’’,67 determined in my paper on the rotation of 
Mars*; and have alfo made proper allowances for the alterations. 
of the geocentric longitudes calculated from the fituations of that: 
planet given in the Nautical Almanack ; by which means. the: 
fidereal is reduced to a proper fynodical period. 
The following three tables contain the refult of the éalcula- 
tions, and ferve to explain the arrangement of. the obfervations 
in the circles. In the firft column are the times when the ob- 
fervations were made. In the fecond, the fidereal places of 
the fpot in degrees and minutes. In the third column are the > 
geocentric longitudes of Mars: at the time of the obfervations.. 
In the fourth, the neceflary corrections on account of thefe 
different longitudes. In the fifth column are the correéted or: 
fynodical places of the fpots; and, according to the numbers. 
in that column,. they are marked on the circles, where con-- 
fequently each {pot is reprefented as it muft have appeared to be - 
fituated at the time of obfervation. 
* Phil. Tranf.vol. LXXE. p 124. 
TABLE 
