82 
rOPL'LAR SCIENCE IlEVIEW. 
the ^vaut of agreemeut between the determination of the sun’s distance^ 
founded on the transit of 1709, and the results which Hansen, Leverrier, 
Stone, 'Winnecke, and Foucault, have deduced from a variety of other 
methods. It was easy to show that the difference, although it amounted 
to three or four millions of miles, yet coiTesponded to an almost infinitesi- 
mally small eiTor in the estimate of the solar parallax. But then the 
method founded on the transit of Venus is precisely such a one as should 
serve to get rid even of so minute an error as this. And indeed the fact 
that astronomers had been in the habit of stating the sun’s parallax as 
8"'5770 showed that they looked on the result as ti’ustworthy to at least the 
third decimal place ; whereas the mean of modern measurements gives the 
parallax as 8' '-9. It is satisfactory to find that the whole error of the com- 
putation founded on the observations made in 1769 may be laid on the effects 
of the peculiar phenomena which attend the egi-ess of a transiting planet. 
Professor Simon Xewcombe had done a good deal towards the solution of 
the problem ; but we believe that the credit of completely accounting for all 
the observations of 1769 in a consistent mamier, with a result according 
closely with that obtained in recent times, must be assigned to Mr. Stone. 
In a paper lately read before the Astronomical Society, he shows that by 
taking the mean between the formation of the black drop ” which precedes 
the second internal contact and the apparent moment of real contact, and 
doing the like for the first internal contact, a result is obtained agreeing 
perfectly with the mean of the determinations obtained by other methods. 
The discovery is important in itself, and doubly important just now, as 
showing what is the principal point to be attended to in the observations 
which are to be made on the transits of 1874 and 1882. 
The PUtnets . — Mercury will be well situated for observation as an evening 
star towards the end of January and until nearly the middle of February! 
Venus will be a morning star throughout the three next months, and well 
situated for observation in January. Mars will be well placed during the 
next quarter, coming to opposition on February 13. His path between 
the two stationary points lies in Leo, being almost equally divided opposite 
the bright star Begulus. On the day of opposition he will be near v 
Leonis. Neither .1 iipiter nor Saturn are very favourably situated for obser- 
vation during the next quarter. Throughout January and February, Uranus 
will be well situated, and will be an interesting object for those possessed of 
first-class instruments. 
Eclipse of the Moon . — There will be a partial eclipse of the moon early in 
the morning on January 28. The eclipse begins one minute before half- 
past twelve, and will end at 2 h. 47 m. A.ir. The gi'eatest phase takes 
place at 1 h. 38 m. a.m., when rather less than half the moon’s diameter 
will be obscured. Interest w'ould attach to the careful spectroscopic analysis 
of the moon’s light during this eclipse, and we trust our observers will not 
lo.*^ the opportunity thus alforded them. 
