522 BIBLIOGRAPHY OF HEESCHEL's WRITINGS. 



Herschel, "W.: Synopsis of the Wkitixgs of — Contiuucd. 



A. D. Vol. P. 



1781 71 121 Two very good clocks were used; one haviug a deal pendulum rod 



and one a compounded one of brass and iron, both, having a i)roi)er 



contrivance not to stoxj when winding up. The rate of going of my 



clocks I determined by the transit of stars. 

 121 Observations on Jiqnter in the year 1778. February 24 — April 12. 



(See Plate V, Figs. 1 to 12, drawings oiJiipitcr.) 



123 Observations on Jnpilcr in 1779. April 14— April 23. See Plate V, 



Fig. 13 [misprinted 18]. 



124 Comparing the observations two and two the following times of one 



synodical revolution : 



gu 54m 5Gs_4 from an interval of 17 revolutions; 



91" 55™ 20^ from an interval of 12 revolutions ; 



9'» 55™ 24^ from an interval of 15 revolutions ; 



gh 55m 4s_(5 from an interval of 41 revolutions; 



gh 55m 403 from au interval of 1 revolution ; 



9I1 54m 5gs,2 from au interval of 29 revolutions ; 



gh 54m 53s_4 fi'om an interval of 26 revolutions ; 



gh 51m 35s from an interval of 12 revolutions ; 



gh 5|m 45s (5 from au interval of 12 revolutions ; 



gh 50m 483 from an interval of 10 revolutions ; 



gu 51m igs_4 from an interval of 22 revolutions; combining the 

 two i^recediug. 

 126 These several results are so various that it is evident that Jupiter is 

 not a iiroper planet for this critical purpose. This great variety 

 cannot proceed from iuaccuracy in the observations; for, in my 

 opinion, it is not possible to make a mistake in the position of a spot 

 which shall amount to 5 minutes of time, as was i)i"oved by the ob- 

 servation of April 23, 1779, 

 126 The synodical revolutions have not been reduced to sidereal ones. 

 126 By a comparison of the different jieriods it ajopears that a spot grad- 

 ually performs its revolutions in less time than it did at first. Ex- 

 amples of this are given. 



126 This is consonant with the theory of equatorial winds. 



127 Observat ions on Mars in the year 1777. (April 8 — April 27. ) See Plate 



VI, Figs. 14 — 19, drawings of Mars. 



128 Observations on Mars in the year 1779. (May 9 — June 17.) Figs. 



20 — 23, drawings of Mars. 

 130 Comparing the observations of 1779 two and two the periods are : 

 24H 3sra ls.5 from an interval of 2 revolutions ; 

 241134m Is. 5 from an interval of 2 revolutions; 

 2411 38m 5s.g from au interval of 36 revolutions ; 

 2411 38m 554 from an interval of 38 revolutions ; 

 241^ 38™ 20^3 from an interval of 34 revolutions. 

 _ 131 Method of reducing synodic levolutions to sidereal (see Fig. 24, dia- 

 gram). 

 133 The sidereal periods from observations of 1777 and 1779 are: 

 24i> 39'" 23^03 from an interval of 768 revolutions ; 

 24'! 39™ 1S«.94 from an interval of 768 revolutions; 

 2i^ 39™ 23^04 from an interval of 763 revolutions. 



134 24'^ 39™ 21^.67 the adopted sidereal revolution of Mars on his axis. 



[Proctor's value, 24'' 37'" 22^715.] 



