358 
SCIENTIFIC SUMMAEY. 
ASTRONOMY. 
Recent determination of the Solar Parallax. — Lately there has been 
published in the Memoirs of the Royal Astronomical Society , an account of 
the final results of the expedition to the Island of Ascension, in 1877, 
organized by Mr. David Gill, now Her Majesty’s Astronomer at the Cape of 
Good Hope, for the determination of the distance of the Sun by means of 
heliometer measurements of the distance of the planet Mars from a number 
of small stars in its neighbourhood. The investigation now published is very 
elaborate, care having been taken to discuss all the probable sources of error, 
so as to show that they cannot have had any effect on the result. 
The final results may be summed up as follows : — 
Value of the constant of the solar parallax when only symmetrically 
placed observations are employed, and certain doubtful observations re- 
jected, — 
7r = 8"*778 ± 0"-012. 
Value of the constant of the solar parallax when all the observations are 
employed, — 
7T = 8"*783 ± 0"*026. 
The mean may be taken as, — 
,r = 8"*78 ± 0"*012. 
This value corresponds to a distance of the Sun of — 
93,080,000 miles. 
This value is much smaller than any other important determination that 
has yet been made, but is confirmed to a certain extent by recent determina- 
tions of the velocity of light, taken in conjunction with the best values for 
the constant of aberration. 
Recently M. V. Puiseux ( Comptes Rendus, March 7th, 1881) has pub- 
lished an account of the results of the observations made by the French 
observers at the Transit of Venus , on December 8th, 1874. The time of the 
passage of the planet over the Sun was observed by eight astronomers at five 
different stations, namely, Pekin, St. Paul’s, Nagasaki, Saigon, and Kobe, 
and when these are compared, they lead to a value for the constant of the 
solar parallax of — 
7r = 8"*96 ± 0"*010. 
