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POPULAE SCIENCE EEVIEW. 
peared entirely. But at the same time a narrow luminous fringe, not of 
uniform breadth or brightness (the latter increasing towards the limb), was 
seen surrounding the moon, but could not be detected on the sun. He like- 
wise tried the effect of pasting a piece of the dark photographic paper across 
the bright lune, and also saw the luminous band at its edges. Professor 
Challis is of opinion that the bands and the fringe are different phenomena, 
the former being due to indistinct vision, whilst the latter is plainly seen. It 
is clear that it is not due to photographic effect, as it has been seen by eye- 
observation, both by Mr. De La Rue and Professor Argelander. It has been 
stated, however, that the same sort of fringe is sometimes observed in photo- 
graphs of mountain scenery along the dark outlines, and it has been surmised 
that it is due to the illuminations of the atmosphere from light reflected 
beyond the dark boundary from the innumerable facets of objects. He is of 
opinion that the corona and red flames cannot be accounted for by the reflec- 
tion of the light of the photosphere from the solar atmosphere, but thinks 
that the ether in its neighbourhood may be so disturbed that it may become 
luminous, and adduces the great height of the Aurora Borealis as a case in 
point, which is sometimes found to be much greater than the supposed limits 
of the earth’s atmosphere. 
Object Glasses of Telescopes. — Mr. Pritchard is of opinion that the new form 
of telescope which was proposed by Gauss, and put in practice by Steinheil, 
and which gives a large aperture with small focus, has nothing peculiar in 
its properties which may not be attained by using the formuhe of Sir J. 
Herschel, published many years siuce. It is remarkable that the latter, 
when calculated in two different ways (which it may be), can lead either to 
the Fraunhofer or Steinheil form, and that “ there are always two object- 
glasses of two different forms which have the same amount of spherical 
aberration for the same material, apertures, and focal length.” The convex- 
concave crown glass of Steinheil corrected by the same form of flint, but in 
which the convex anterior surface of the object-glass is less curved than the 
other, which is concave, co-exists with that of Herschel, composed of a double 
convex crown, corrected by concave flint. Mr. Pritchard considers that the 
ordinary Herschel form is preferable to that of Gauss and Steinheil, as a 
very slight error of radius in the flint lens of the latter would destroy the 
goodness of the object-glass. Mr. Pritchard advises the imperative necessity 
of a careful determination of the indices of refraction of the glass employed, 
an error of the third decimal place being quite sufficient to endanger its per- 
formance. He is of opinion that the thickness of the lenses is not so 
material, but that when the diameter of the glass exceeds six inches, great 
care is necessary even in this respect. 
New Planet . — The latest discovery in this branch is the planet (81) which 
was detected by M. Tempel, at Marseilles, on Sept. 30. It has received the 
name of Terpsichore, and when first seen was estimated of the 10th mag- 
nitude. 
Comets . — The comet discovered by Professor Donatis, at Florence, on 
Sept. 9, and which is the third found this year, passed its perihelion on 
July 27. The second comet of 1864, discovered by the same astronomer, on 
July 23, passed its perihelion on Oct. 11, 1864. 
Self-registering Thermometer. — Mr. Hamilton, of Liverpool, has invented a 
