98 
POPULAR SCIENCE REVIEW. 
better instruments ; but as much depends on the steadiness of the sun 
and absence of tremor in the atmosphere, they u can scarcely be entirely 
avoided. Even at the same place of observation, as at Paris, Greenwich, 
London, and Oxford, the difference of the times of contact of the margins 
of Venus and the sun, as given by different observers at those places, 
varied between sixteen and twenty-five seconds. By the proposed increase 
in the solar parallax, the earth is brought closer to the sun by four millions 
of miles, and the annual path of the earth is diminished by some twenty- 
five millions of miles, so that it does not travel at such a rapid rate as was 
formerly supposed. The distances and dimensions of all the planets are 
similarly decreased (as expressed in miles), that of the moon, however, 
remaining as before. These are matters of simple curiosity, but even a 
slight change in the actual parallax of the sun will produce but little 
effect in the most delicate investigations of practical astronomy. From 
the combination of the Williamstown and Greenwich observations of 
Mars, as made by Mr. Stone, the extreme values of the parallax are 
9"*65 and 8"*50, the mean result of all being 8"*932, and the probable 
error 0"*032. 
Occultation of Kappa Cancri. — In the last summary the phenomenon of 
an interruption in the light of this star at the moment of immersion 
was mentioned as witnessed by Mr. Copeland. The occultation was 
fortunately seen by several observers. Captain Noble writes that he 
observed it with an excellent telescope by Ross, of 4^-inch aperture, but 
did not perceive any diminution of its light. Mr. Vertu, who saw it at 
Nottingham, says that he followed it until in contact with the moon’s 
edge, when it disappeared instantaneously. This observer states, that 
although the moon was nine days old on this occasion, the complete circle 
of its disc could be traced, and even some features in the dark part were 
discernible, and thinks that the impression of the diminution of light was 
due <( to the excitement produced on the retina by an intense and protracted 
gaze at the object.” 
Klinkerfues’ s Comet. — This, the second comet of 1863, is still visible, but 
from its great distance from the earth is exceedingly faint. Its position 
on Oct. 1 is R.A. 12 h 7 ra , declination 57° 35' north. It has then only 
one quarter of the brightness which it possessed on July 15, when it was 
waning in lustre. 
Mars . — Mr. Lockyer took advantage of the favourable position of 
Mars at its last approach to the sun and earth to make a complete 
examination of its surface, and to compare it with the map made by Beer 
and Maedler in 1830, on which occasion it was nearly under the same 
conditions. It is satisfactory to learn that, with the exception of a few 
slight and fleeting changes, which he considers as due to the transit of 
clouds over the planet, all the features noticed by the earlier observers 
were reproduced in the most marvellous manner ; and although Mr. 
Lockyer had the more powerful telescope, yet it only served to show the 
old details more plainly. The changes noticed were principally in the 
tones of the different parts of the planet, both light and dark, which he says 
occur daily, if not hourly. 
Companions of Sirius. — The minute points of light detected by the 
