cclxxxviii RESULTS. 



those peculiarities of detail which have already found expression in the computation, the dispro- 

 portion will be yet further increased. The distance of Mars at the second opposition was greater 

 than at the first by nearly 15 per cent ; the proximity of Venus to the sun was accompanied by 

 serious disadvantages, and still other influences combined to render the first series upon Mars 

 decidedly better adapted for attaining the desired end. 



All these considerations concur to support the opinion already expressed, that the results of 

 the first Jfars-series should be regarded as the results of the expedition, and that the value 



J- = O."0762 

 should be accepted as the best which the observations will afford. 



The combination of the three other series, independently of this first one, furnishes values 

 indicating a much larger diminution, whatever method of combination may be employed. The 

 four different principles for estimating the relative weight conduct to the four following values 

 of *", as deduced from the second Jfars-opposition, combined with the two conjunctions of Venus. 



Weights. <Jw 



(n r + n") e * - O."1332 



n' e~* O."1360 



n e- 2 - O."1844 



v O."1769 



Adopting, then, as final the value given by the first Mars-series, we have 



* = 8."5712 O."0762 = 8."4950 ; 

 according to which we may assume with advantage, 



The sun's equatorial Iwrizontal parallax 8."5000 ; 



being less by O."07 than the value commonly adopted, and corresponding to a distance of 

 24 266 terrestrial semidiameters, 96 160 000 statute miles, or 15 475 000 myriameters. 



