te of the it of the year in whic i jas se were 
al list of comparison-stars thus constructed, containing 
rit only the declinations of each star, but the i i value of the de- 
rmination 
The complete. reduction of all the observations was then repeated, and 
the several‘comparisons with each star consolidated with care into a single 
observation, of which the weight was determined, and which was sub- 
ent treated like an absolute a of place, and even com- 
| with meridian observations. Eac e four series (viz. the two 
4. Toeneions and the 5 saaneoecr it was treated independently, 
the ertor of the ephemeris considered as of the form 2-+ ty-+- 1°2, 
* denoting the time from a medial epoch. Four other unknown quanti- 
The ae indicates that the results afforded by the series of observa- 
tions of Mars, duri ring the opposition of 1849-50, so far surpass any 
the others in precision and_ trustworthiness, that these, taken alone, 
a closer ci. ga to the desired values than when combined with 
tee other 
The resultant delecinkistioas of the whole discussion are as follows: 
ul Wt 
Semidiameter of Mars = 4-6639-+1'9681 — 6°63 
“ Ve = 86625 — 03118 = 8°35 
Mean Solar Parallax == 85712 ~ 00762 = 84950 
The great increase of the reviously assumed semidiameter of Mars is 
be srkin ng. It has tive impracticable in most cases to free the 
thediameter from the possible influence of an irradiation dependent on 
eles a 
ions onl 
the the previously adopted alte? is inated by six series of ob- 
trvations being all made,. — = first opposition, with the excep- 
of the Cape of Good Ho ope se 
The 8 sig of a small daainttid of the et ihe diameter of Venus 
So to be distinctly and strongly pointed out. 
i value of the parallax I am not nee to place 
tie, great stress, but cannot refrain from expressing the decided convic- 
iawn ae value obtained by Encke from the agile Venus i E ig 1 
may be improved by a slight dec and am inclined to 
aul eo value 8”” bod as tee in all preity quite near the truth, 
wh — value may be advantageously adopted. G. 
ND SERIES, Vor XXVI, No, 80.—MARCH, 1859. 
37 
