SCIENTIFIC SUMMARY. 
359 
It will be remembered that tbe results of the English observations, which 
were founded on the time at which the planet touched the limb of the Sun, 
and not on the duration of the transit, gave results of little value, for by 
putting perfectly reasonable but somewhat different interpretations on the 
descriptions given by different observers, there could be obtained any value 
of the solar parallax between — 
7r = 8"-90. 
and — 
7t = 8"-75. 
Mr. Stone has criticised the results given by M. Puiseux ( Monthly 
Notices, April 1881), and he is of the opinion that two of these durations, 
namely, those of MM. Janssen and Tisserand, must be rejected as incom- 
patible with the interpretation placed on them. The remaining six then 
give a value of the constant of the solar parallax of— 
tv = 8 "- 88 . 
The English photographs of the Transit of Venus failed totally, as had 
been predicted by more than one astronomer before the Expedition went out 
in 1874. The Americans relied on another method of applying photography 
to this purpose, and they seem to have obtained results of far greater accu- 
racy. Lately, Mr. D. P. Todd, of Washington, has published an account of 
the results which have been so far obtained. At the three northern stations, 
Wladiwastock, Nagasaki, and Pekin, eighty-four photographs were obtained; 
and at the five southern stations, Kerguelen Island, Hobart Town, Campbell- 
town, Queenstown, and Chatham Island, 131 photographs were obtained. 
From a discussion of the distances of Venus from the centre of the Sun, the 
value of the solar parallax was found to be — 
7r = 8"-888 ± O''- 042. 
From a discussion of the position angle at which Venus was situated, 
there was obtained the value, — 
7T = 8"*873 ± 0"*060. 
From both classes of observations the result is — 
7r = 8"*883 ± 0"-034, 
corresponding to a distance of the Sun from the Earth of — 
92,028,000 miles. 
It will be seen, therefore, that the results obtained by these two methods, 
the Transit of Venus and Opposition of Mars, give results differing by more 
than a million of miles, and much remains to be done before the value of the 
solar parallax, or distance of the Sun, can be regarded as known with any 
degree of certainty. 
In the meantime, other and improved methods of determining this im- 
portant factor continue to be carried on. Prof. Newcomb is engaged on 
a new determination of the velocity of light ; Mr. Gill is understood to be 
engaged on preparations for a new determination of the parallax from 
observations of the minor planets; at Pulkowa there is being made a fresh 
determination of the time taken by light to traverse the terrestrial orbit, from 
the data afforded by the observations of the eclipses of Jupiter's satellites ; 
