1875.] ( 169 ) ' 
Ill. THE LATE TRANSIT OF VENUS: 
By RicHarp A. Proctor, Author of ‘* Past and Coming 
Transits,” &c. 
T the moment of writing, news has been received from 
all the stations selected for observing the late transit, 
excepting two French stations—St. Paul’s Island 
and Campbell Island—and though as yet the news from 
most of the stations is far too imperfect for any attempt to 
be made to calculate the solar parallax, while from others we 
only have news that observations were successfully made or 
otherwise, yet we know enough already to be able to form an 
opinion as to the general success of the operations. The 
result cannot but be considered as on the whole extremely 
favourable. It was certain, or all but certain beforehand, 
that there would be fine weather at some of the stations and 
bad weather at others; and the feeling was universally 
entertained amongst those best competent to judge that, if 
fine weather prevailed at half the selected stations, astro- 
nomers would have every reason to be satisfied, provided 
always that the fortunate stations were not all in one or two 
regions, or in the same hemisphere. It was also considered 
that, if one half of the various methods on which reliance 
was placed should succeed, the result would be quite satis- 
factory. It will appear, from the facts I am about to bring 
before the reader, that these hopes have been much more 
than fulfilled. A large proportion of the stations had 
weather either altogether favourable, or sufficiently so to 
enable the observer to secure satisfactory results ; while all 
the methods proposed for observation have been successfully 
applied (unless the Janssen turning-wheel arrangement be 
regarded as a distin¢ét method rather than a modification of 
Delisle’s). 
For convenience, it will be well to consider the several 
methods separately, rather than to take the stations in 
order—in fact, no otherwise can clear or satisfactory ideas 
be obtained of the success of the whole plan of operations. 
We may consider the methods in use as divided into three 
broad classes—the Delislean, the Halleyan, and the mid- 
transit method. This classification includes the photographic 
and heliometric operations, as well as the spectroscopic 
method for observing external contact. For, both pho- 
tography and heliometry may be regarded as means for 
determining the position of Venus at given instants, either 
