SCIENTIFIC SUMMARY. 
303 
bright lines and continuous spectrum, which would exist on Mr. Stone’s 
hypothesis; (2) the star-clusters just within the resolving power of the 
largest telescopes do not give, even faintly, a spectrum of bright lines ; and 
(3) the same bright lines appear to be common to all the nebulae which 
give a bright-line spectrum, whereas on Mr. Stone’s hypothesis, differences 
of constitution of the enclosing atmospheres of different star-groups would 
be probable. Towards the close of his reply, Dr. Huggins indicates the 
objection we have above enforced, and mentions that this objection was 
strongly insisted upon by Professor Stokes in remarks made when Mr. 
Stone’s paper was read. 
Supposition that Sunlight can he condensed . — Similar in incorrectness to 
the supposition that the brightness of an irresolvable stellar cluster can be 
diminished by distance, is the belief that under any circumstances sunlight 
(or other light from a luminous disc or surface) can be strengthened or con- 
densed. It is singular that this mistake should have been fallen into by 
the present first assistant at Greenwich almost at the same time as the late 
first assistant enunciated the theory above discussed. A paper, too prepos- 
terous to be here dealt with, had been read before the Astronomical Society, 
suggesting that Venus has a metallic surface and a vitreous atmosphere. 
Deferring to this paper, though of course rejecting the metallic surface and 
glass envelope, Mr. Christie pointed out that a mirror surface and an atmo- 
sphere capable of interior specular reflection, or the first alone with an 
ordinary refractive atmosphere, would explain the fact (P) that the arc of 
light seen round Venus in transit is brighter than the sun itself. Oddly 
enough a reply was made to this to the effect that a mirror surface was not 
needed for the purpose, but that ordinary refraction in the atmosphere of 
Venus would very much condense the sun’s light, by compressing the whole 
disc of the sun into a fine arc of light around the outer limb of the planet. 
In point of fact, it is utterly impossible to condense light in this or any 
other way. As Mr. Proctor has shown, in a paper read before the June 
meeting of the Astronomical Society, by whatever process the breadth of 
the luminous surface is diminished (i.e. the axes of pencils proceeding from 
different parts of it brought nearer to parallelism), by the same process and 
to the same degree, the pencils themselves are made more divergent ; thus 
a given portion cf the retina receives pencils of light from a wider area of 
the sun’s surface, but the quantity of light received from each pencil is in 
the same degree diminished. The arc of light seen round Venus was 
simply brighter than the neighbouring part of the sun’s disc, because that 
light came from the whole of the sun, and the central part of the sun’s disc 
is brighter than the part near the edge. 
Distances of the Stars. — Mr. Stone, Astronomer-Royal at Gape Town, has 
gone over a portion of the evidence relative to the distribution of the fixed 
stars with respect to distance. It is singular that a matter so well-worn 
should still attract the attention of astronomers, more especially of official 
astronomers, whose duties in reality have no relation to such questions. u It 
may have been shown,” says Mr. Stone, referring to Mr. Proctor’s researches, 
u that some astronomers have attached undue importance to the numerical 
accuracy of the results obtained by W. Struve ; but I cannot consider that 
the average distribution of stars according to apparent brightness has been, 
