534 BIBLIOGRAPHY OF HERSCHEL's WRITINGS. 



Herschel, W.: Synopsis of the Writings of— Continued. 



A. D. Vol. p. 



1783 73 277 [Foot-note.] And slionld there ever be found, in any particular part 

 of the heavens, a concurrence of proper motions of quite a difierent 

 direction we shall then perhaps begin to form some conjectures as 

 to which stars may possibly belong to ours and whicn to other 

 systems. 



278 Discussion of the data of the tables. 



279 The general law according to which the declinations of the stars are 



governed is this : Let an arc of 90° be applied to the sphere of the 

 fixed stars so as always to pass through the apex of solar motion. 

 Then wliile one end of it is drawn along the equator the other will 

 describe a closed curve. The law is that all stars in the northern 

 hemisphere situated within the nodated part will seem to go to the 

 north by the motion of the solar system ; the rest will ajjpear to go 

 southward. A similar law applies for the southern hemisphere. 

 See Fig. 5 and Fig. 6 and the explanation, p. 280. 



281 A paragraph of Mayer's [quoted] which seems to contain an objec- 

 tion against the solar motion is really a good argument in its favor, 

 as is shown. Mayer's paper was read in 1760, and mentions the 

 motion of the solar system as a very possible thing, and points out 

 some of the consequences of such a motion. 



283 The foot-note gives a reference to two other papers of the same sort, 

 one by Wilson (1777), and one by Lalande (1776). 



1784 74 233 On the remarkable appearances at the polar regions of the planet Mars, the 

 inclination of its axis, the position of its poles, and its spheroidical fig- 

 ure; with a few hints relating to its real diameter and atmosphere. By 

 William Herschel, Esq., F. R. S. Read March 11, 1784. 



234 The polar spots of Mars may aiibrd a good means of "settling the in- 



clination and nodes of that planet's axis." It was a question to be 

 settled by observation how far these spots were permanent and iu 

 what latitude of Mars they were situated. 



235 Observations from 1777, April 17, to 1783, Nov. 11. See Plate VI, 



where there are 24 drawings. 



237 1783, May 20. The polar spot, which is bright, seems to project above 



the disk by its splendor. 



238 [From observations up to 1783, Sept. 25.] I concluded that none of 



the bright spots were exactly at the poles, though not far from them. 



241 Appearances explained by graphical constructions, Plates VII, VIII, 

 IX, X. 



243 Table giving the synodical places of the spots at the times of the dif- 

 ferent observations. 



247 Of the direction or nodes of the axis of Mars, its inclination to the ecliptiCf 



and the angle of that planeV s equator with its own orbit. 



248 Observations of angle of position of the polar spots. 

 252 Method of correcting the observations. 



254 Table of resulting corrections. 



254 From 13 observations reduced to 1783, October 4, the position of the 



axis of Mars was 55° 41' s.f. 

 256 From 2 observations reduced to 1781, June 25, this position was 75° 



11' 8. p. 

 256 The north pole of Mars must be directed towards some point of the 



heavens between 9 s. 24° 35' and s. 7° 15'. 

 258 Method of reducing the elements from the ecliptic to the orbit of Mars. 



