544 On the Motion oj the Sun and Solar Sy stein. 



■ By these ans;le3, with the assistance of the lii^es sa,- 

 whose lengths represent the annual quantity of the appa- 

 rent motions as given in our former tabic, the figure No. 2 

 has been constructed. When the situation of these angles 

 is regulated as in that figure, we may draw the several lines 

 ma perpendicular to S P, and, by computation, their value- 

 and sum will be obtained as follows : 



Table V. 

 Quantities and Sum of the least real Motions. 



Sirius - - 0,65432r 



Arcturus - - 1,58784 



Capella - - 0,10887 



Lyra - - 0,11281 



Aldebaran - 0,01104 



Procvon - - 0,04 99S 



Sum 2,2!2491'' 



The result of this itivestigation is, that by admitting a 

 motion of the. sunl towards A Herculis, the annual proper 

 iTiotions of our six stars, of which the sum is 5,353 7'^, may 

 be reduced to real motions of no more than 2,2249". 



When first I proposed A Herculis as an apex for the solar 

 motion, it may be remembered that a reference to future 

 observations was made for obtaining greater accuracy *. 

 Such observations we have now before us, in the valuable 

 tables from which I have taken the proper motions of the 

 six stars; and I shall prove tlvat, with their assistance, we 

 may fix on a solar motion that will be considerably more 

 favourable. 



We have already shov/n, that to ascertain the precise 

 place of the best apex is attended with some difficulty; bat 

 from the inspection of the figure which represents the quan- 

 tities of real motion required when A Herculis is fixed upon, 

 It will be seen that, by a regular method of approximation,, 

 ue may turn the line SP into a situation wliere all the angles 

 of the apparent motion of the six stars will be nmch reduced. 

 The quantities which are required for constructmg another 

 figure to represent the threefold motions of our six stars, 

 w hen a different apex is fixed upon, are to be found by the 

 same method we have pursued in the instance of'A Herculis; 

 and the figure that has been given with respect to that star, 

 shows evidently that the parallactic line S P should be turned 



♦ See Phil. Trans, for 1783, p. 27'i, line 8 ; and p. £T4, line 4. 



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