of Edinburgh, Session 1870-71. 
461 
brighter than the photosphere (IV.), and, finally, no light but that of these 
gases is intense enough to reach us (VI.) That there is energy enough to 
produce these successive developments is obvious from the fact that, even 
at their immense distance, the visible portions of the nebulae of Orion and 
of Argus subtend an angle of nearly four degrees. 
Application of the spectroscope to determine the relative velocity of 
A STAR, OR OF A GASEOUS CURRENT IN THE SOLAR PHOTOSPHERE, WITH 
REGARD TO THE EARTH. 
Analogy from sound. 
Railway whistle. 
Tuning-fork experiment. 
Similar experiment with organ-pipe. 
Finally, absorption by bodies at ordinary temperatures. 
Coloured glasses. 
Chlorophyll. 
Detection of blood, changes of the blood-spectrum by 
oxidation, &c., &c. 
Microscopic spectroscope. 
The following Communications were read : — 
1. Note on the Early History of Spectrum Analysis. By 
H. Fox Talbot, Hon. F.B.S.E. 
Newton, in his observations on the spectrum, appears never to 
have used a narrow aperture. In fact there was nothing, in the 
existing state of knowledge in his day, to lead him to suppose that 
this would alter the phenomena. 
Wollaston was the first who observed some obscure bands in the 
spectrum, by viewing with a prism the aperture left by the shutters 
of his room when nearly closed. It is surprising that this acute 
philosopher did not follow up the hint thus accidentally presented 
to him, but contented himself with the rude observation above 
mentioned. 
Fraunhofer was the first who detected the wonderful system of 
dark lines in the solar spectrum, by viewing a very narrow and 
accurately formed aperture with an excellent prism, aided by a 
small telescope. He likewise gave names to the principal dark 
lines which have been generally adopted, and he measured accu- 
rately their refractive indices by mounting the prism on a 
graduated brass circle movable round a centre. 
After completing his observations on the solar spectrum, be 
3 Q 
VOL. VII. 
