Secular Changes in the Solar System. 23 



36*00016 inches of Sir George Shuckburgh's scale, in which 

 Capt. Kater's measures were originally taken. 



In these L is the length of the sexagesimal pendulum, and 

 I that of the decimal metrical pendulum. 



These have been added to this paper for the convenience of 

 comparing the British and French measures. 



I am, gentlemen, yours &c. 



Edinburgh, Nov. 11, 1824. WiLLlAM Galbraith. 



IV. Ott the Annual and Secular Changes in the Solar System, 

 By A Correspondent. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



nPHE inclosed paper is offered for the purpose of pro- 

 -■• moting inquiry on a point materially affecting the accu- 

 racy of the solar tables : if it appear to you worthy the atten- 

 tion of your readers, you will oblige the author by inserting 

 it in your valuable Journal. 



I am, gentlemen, yours &c. 



C. 



Having remarked that a secular diminution of 42"-67 an- 

 swered better than any other I had tried for the secular 

 change of the obliquity of the ecliptic, I was induced to 

 examine whether the masses of Venus and Mars, altered to 

 suit it, would represent with any degree of accuracy the an- 

 nual and secular changes in the other phaenomena of the solar 

 system proceeding from the action of the planets. I accord- 

 ingly collected all the observations of the nodes and aphelia 

 of the several planets' orbits I could procui'e, and from their 

 comparison estimated as nearly as I could the annual change 

 in each. 1 then calculated, upon Laplace's hypothesis of the 

 masses of the planets, their respective perturbations from the 

 formulae in Woodhouse's Astronomy, and then changed those 

 of Venus and Mars to suit my hypothesis of the change in 

 the oblicjuity; and the close coincidence of the results with 

 observation have determined me to lay them before the 

 readers of your valuable Journal, 



The following are the principal of the observations which 

 I procured, many of them having been rejected for giving re- 

 sults differing much from the mean ; but upon the whole I 

 cannot say that I place too much reliance on any of them; so 

 that when my calculations give a number within the two ex- 

 tremes 



