SCIENTIFIC SUMMARY. 
305 
municate their observations to him, to enable him to perfect Mr. Proctor’s 
chart of the planet. 
The Astronomer-Royal has also invited attention to observations in con- 
nection -with the determination of the solar parallax, which might advan- 
tageously be made at the approaching opposition of Mars. He cited, from 
the “Monthly Notices” of 1857, his paper “On the means available for 
correcting our measures of the sun’s distance during the next twenty-five 
years,” in which, alluding to Flamsteed’s method by observing the displace- 
ment of Mars in right ascension when he is far east and far west of the 
meridian, and pointing out its facilities, he had concluded that this method 
is the best of all. “ An unexpected opportunity,” he continued, “ of 
obtaining observations, probably of a much superior class, has presented 
itself. Lord Lindsay is willing to lend his heliometer; and Mr. Gill, v?ho 
has had extensive experience in the use of that instrument, and is perfectly 
acquainted with its adjustments of all kinds, offers his own time and labour 
at St. Helena or Ascension.” He then referred to the probable expenses 
of the expedition. Since then, the sum necessary (500/.) has been granted 
by the Astronomical Society, one-half to be eventually repaid, either from 
the Government allowance to the Royal Society, or by Lord Lindsay and 
Messrs. De la Rue and Spottiswoode. The place since selected by Mr. Gill is 
the Island of Ascension, where the weather is likely to be more suitable 
than at the Mauritius. A rigid determination of the planet’s heliocentric 
positioi; will be among the objects of Mr. Gill’s observations. 
The Total Eclipse of the Moon last February. — Mr. Penrose remarks that 
during totality the northern and southern parts of the moon appeared very 
much brighter than the eastern and western parts; adding that this “pre- 
sumably arose from some interference with the light refracted through the 
earth’s atmosphere, from a greater prevalence of clouds in the equatorial 
regions than at the two poles ; some amount of specular reflection, at 
very flat angles from the northern and southern ice, may also have aided in 
producing this effect.” Mr. Penrose is so thorough a master of the geo- 
metry of eclipses, and so well able to calculate the amount of light falling 
upon various parts of the moon from the irregular ring of light which must 
appear to surround the earth as supposed to be seen during totality from the 
moon, that we cannot doubt the above sentence was penned without much 
thought; for it is certain that the light from various parts of that irregular 
ring is mingled and in nearly equal proportions over all parts of the moon’s 
eclipsed hemisphere, not distributed locally. The mistake of attributing 
the different degrees of light on various parts of the eclipsed moon to this 
cause is as old as Wargentin, if not older. Probably Mr. Penrose had 
noted it in some of the older descriptions of eclipses without perceiving that 
it is erroneous ; and naturally enough quoted it, without remembering that 
he had not closely examined it. 
Rev. Fr. Perry remarks that the thin circle of light on the moon’s limb 
was in such striking contrast with the cloudy dull brick-red shading of the 
centre that to many persons it seemed as if the moon was not completely 
immersed in the earth’s shadow. Fr. Perry and Mr. Penrose formed, by the 
way, entirely different views respecting the definiteness of the umbra’s out- 
line. Fr. Perry says, “ the darkness of that portion of the penumbra which 
