surrounded by a luminous atmosphere, may be looked upon as so many opaque, habitable, planetary globes; differing, from what we know of our own planets, only in their size, and by their intrinsically luminous appearance. They also, like the planets, shine with differently coloured light. That of Arcturus and Aldebaran, for instance, is as 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 γ Andromedæ, β 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 1st 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.
"α Orionis contains the same colours, but the red is more intense, and the orange and yellow are less copious in proportion 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.
"Aldebaran contains much orange, and very little yellow.
"α Lyrae contains much yellow, green, blue, and purple."
