264 
POPULAR SCIENCE REVIEW. 
star 222 Arietis, great changes have taken place since 1834, — the principal 
star of the sixth magnitude, and visible to the naked eye, having vanished 
completely; whilst the three others, which in 1834 were of the fifteenth, 
tenth, and ninth magnitudes respectively, when viewed through the Elchies 
telescope, were found to he two of the twelfth, and the last of seven and a 
half magnitudes. This may serve as an example of the continual and 
usually unnoticed changes which are taking place in the heavens. As a 
crucial experiment of the defining power of the telescope, it may he stated 
that the blue star of Gamma An dro medic was completely and more than 
separated. Scarcely more than half a dozen of the best instruments in the 
world at the present time would he able to effect this separation. 
Great Comet q/lSfil. — The Rev. Mr. Webb has recently given the result 
of his observations on the comet of 1861, in regard to the nucleus, 
envelopes, the luminous sector or fan, the coma, and the tail. The en- 
velopes were the most remarkable portion of the comet, particularly on 
the night of June 30, when the effect produced was compared to a number 
of light, hazy clouds, floating around a miniature full moon, and when 
portions of six of various lengths and degrees of curvature could be distinctly 
traced. From a general resume of his observations made up to July 23, 
Mr. Webb is of opinion that as no phase was visible in the nucleus, that 
this part “ either contained no concentration of opaque matter or shone 
by intrinsic light.” The axial rotation of the nucleus also seems im- 
probable, but it would appear probable that there was some amount of 
libration if we were to judge by the swinging motion of the sector. The 
latter was of later date than the envelopes and much posterior to the 
perihelion passage ; as the comet retreated from the sun, the envelopes 
descended on the nucleus, and caused perhaps the increasing apparent 
density of the whole coma. No indications of rotation were perceived 
in the tail. The angle which the sector and envelopes made with the axis 
of the tail would lead one to suppose that a stronger repulsion or a less 
resisted emissive force acted in one direction from the nucleus than in the 
opposite. The nebulous veils were always seen better on one side than on 
the other, but from the position of the comet in its orbit no satisfactory 
deductions can be made in this respect. 
According to wishes expressed by correspondents, we append the elements of 
the first and second comets of this year. — The first, discovered by M. Schmidt, 
at Athens, on J uly 2, near the stars Beta, Rho, and Sigma Cassiopeise, 
was at its shortest distance from the sun on June 22, 5 1 43, Greenwich 
mean time. The longitudes of node and perihelion were respectively 
324° 30' and 298° 35'. The inclination was 8° 14', the motion retrograde, 
and the logarithm of least distance 9 - 992. The second comet of 1862 passed 
its perihelion on August 23, 7‘1 Berlin mean time, the longitudes of 
node and perihelion being 137° 5' and 344° 164', the inclination of 
orbit 66° 3' ; motion retrograde, and the logarithm of least distance 
being 9'985. 
Companion to Procyon . — The existence of dark stars in the heavens, 
which controlled the motions of those visible to the eye, which idea is due 
to Bessel, was good-humouredly ridiculed by Humboldt in his corre- 
spondence with the former. It is now, however, made a matter of 
