2 ^ 4 ) Herschel's Astronomical Observations 
different from the light of Sirius and Capella, as that of Mars 
and Saturn is from the light of Venus and Jupiter. A still 
greater variety of coloured star-light has already been shewn 
to exist in many double stars, such as y xVndromedae, jG Cygni, 
and many more.* In my sweeps are also recorded the places 
of 9 deep garnet, 5 bright garnet, and 10 red coloured stars, 
of various small magnitudes from the 7th to' the 12th. 
By some experiments, on the light of a few of the stars of 
the first magnitude, made in 1798, by a prism applied to the 
eye-glasses of my reflectors, adjustable to any angle and to 
any direction, I had the following analyses. 
The light of Sirius consists of red, orange, yellow, green, 
blue, purple, and violet. 
a Orionis contains the same colours, but the red is more 
intense, and the orange and yellow are less copious in pro- 
portion than they are in Sirius. 
Procyon contains all the colours, but proportionally more 
blue and purple than Sirius. 
Arcturus contains more red and orange and less yellow in 
proportion than Sirius. 
iUdebaran contains much orange, and very little yellow. 
a Lyrae contains much yellow, green, blue, and purple. 
The similarity of the general construction of the sun, the 
stars, and the planets, is also much supported by the periodical 
variations of the light of the stars observed in many of them ;-f 
for these variations can only be satisfactorily accounted for by 
admitting such stars to have a rotatory motion on their 
* See Catalogue of double stars Phil. Trans, for 1782, III, 5. V> 5, &c. 
f See Mr. Pigott’s Catalogue of variable stars Phil. Trans, for 1786, page 
