ON LIGHT, 381 
O Neon bG Har, 
Parr I. 
ABSTRACT OF MR. W. SQUARE’S, JUN., PAPER. 
(Read October 22nd, 1874.) 
Lieut was shown to consist of vibrations of definite length and 
velocity. That time was expended in the passage of light was 
explained by Olav Reemar’s observations of the satellites of Jupiter, 
by Bradley’s theory of aberration, and Fizeau’s wheel. The laws 
of reflection and refraction were explained. Colour was shown to ~ 
consist of rays of light simply differing in the relative length and 
velocity of their waves. ‘The relations of the colours among them- 
selves were explained; the complimentary colours, when mixed, 
made white. ‘he chromatic scale of colours was proposed by M. 
Chevreul as a great improvement in the arts; the whole, mixed, 
made white. The theory of the colour of various objects was 
discussed, and the quenching of some of the returning rays shown 
to be the cause of their colour. -It was experimentally shown how 
some rays quenched others. The division of white hight into its 
various constituents was shown by means of bisulphide of carbon 
prisms. The spectra of various metals were exhibited, and Kirchoff’s 
reversal of the D line. This was shown to be the cause of the 
production of all the Fraunhofer lines. Maps of these lines were 
shown illustrative of their number and order. The spectra of 
various gaseous substances were shown. The spectra of stars 
differed. They were regularly classed, the prime element in their 
classification being the fact as to whether they contained hydrogen 
or not. It was shown that planets differed much. Mars was like 
our earth in composition, while from spectroscopic observation it 
was inferred that Saturn was still in a highly-heated condition, and 
not habitable. The light from Jupiter, Saturn, and Uranus differs 
much from that of Mars, and the facts deduced from these differences 
have high astronomical importance. Many of the stars have spectra, 
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