524 Notices of Books, [October, 
“ii. Why the orbits of the planets and satellites have become 
elliptical. 
“ 12. The reason why the orbital planes of the planets are not 
in the equatorial planes of the sun ; why the orbital planes of the 
satellites are not in the equatorial planes of the planets ; why 
the axes of the planets and satellites are not perpendicular to 
their orbital planes; and why the rotation of Uranus, and possi- 
bly that of Neptune is retrograde. 
“ 13. Why the inner rings of Saturn remain unbroken. 
“ 14. The explanation of the ring of the asteroids, probably 
many hundred small plants in a belt by themselves. 
“ 15. The explanation of the origin of the milky way. 
“ 16. Why all planetary and solar systems move rapidly 
through space, and why all sidereal systems are stationary.” 
The author also seeks to demonstrate the cause of 
stellar light and heat to be chemical aCtion. From his remarks 
on this subject we take the following extracts: — “The ignition 
of meteors proves that our air extends considerably higher than 
205 miles. Even before reaching that point the amount of 
latent heat in the upper regions of the air is something wonder- 
ful. When this very rare air is compressed in front of a 
swiftly-shooting meteorite, the repulsion is overcome and the 
heat becomes sensible. The air is then heated to ignition, and 
often vitrifies the surface of the meteorite. In my paper on 
‘ Meteors,’ published in the * Proceedings of the American Asso- 
ciation for the Advancement of Science,’ 1871, I have given 
examples of meteors which have been known to travel horizon- 
tally a thousand miles and more through the upper strata of the 
atmosphere, and continue vividly bright through the whole dis- 
tance. I gave also examples of other meteorites which came 
down nearly vertically, and, although in broad daylight they 
glowed when high up as brightly as the sun, nevertheless their 
light was invariably extinguished before reaching the earth. 
Had the meteors themselves been incandescent, their brightness 
would have continued another twinkling of the eye until they 
struck the earth. Meteors are bright in the upper regions of the 
air, because of the abundance of latent heat up there. Their 
brightness goes out in the lower and denser strata of the air, 
because there is much less latent heat, although the friction is 
so much greater.” He then contends that it is impossible for 
us to say how much chemical force can be stored up in the 
unknown chemical elements in the sun, or in their compounds. 
He declares that “ the very greatest of all the lessons taught 
by the spectroscope has hitherto been overlooked by scientific 
men ; this lesson is the wide difference between the earth and 
the sun as regards their simple elements.” Spedtroscopists also 
let slip another truth, which is that “ there are thousands of 
fixed lines in the solar speCtrum which are perfect strangers 
to us.” 
