42 REPORT—1857. 
lions of years would be required to cause a reduction or one per cent. in the momenta 
of these vast bodies. I must however question the results of Laplace, who finds that 
the change in the length of the day has not amounted to the 745th part of a second 
during the last 2000 years. This conclusion is based on a comparison of ancient and 
modern eclipses ; and the time of the earth’s rotation is thus ascertained from the 
revolutions of the moon, making corrections for the disturbances operating on the 
latter body. Butall the disturbing influences have not yet been taken into considera- 
tion; and as the one noticed in the present article operates on the earth and moon, 
we cannot regard either of these bodies as an infallible chronometer for measuring 
the vast ages of eternity. 
On the Light of Suns, Meteors, and temporary Stars. 
By D. Vaueuan, Cincinnati, Ohio. 
Modern science recognizes shooting-stars, fire-balls, and meteoric stones as bodies 
which enter our Ely 35 from external space with immense velocities. From the 
great elevation at which these objects are Juminous, it has been inferred that their 
light has little or no dependence on aérial action ; and indeed the presence of the air 
alone could not account for the greatness of the illumination which marks their ap- 
et to the earth, but ceases when they enter the dense stratumsf the atmosphere. 
The diameter of many luminous meteors has been estimated at two or three thousand 
feet ; and the globe of light which they exhibited must have been several million times 
greater than the largest meteoric stone yet found on the earth’s surface. It is sup- 
posed that these brilliant exhibitions are produced by cosmical masses several hundred 
yards in diameter, which, in traversing the planetary regions, occasionally sweep 
through the verge of our atmosphere, and, after casting a few fragments on the earth, 
continue their course through space. But the idea that such wandering bodies should 
graze our planet so often, without ever striking it directly or falling to its surface, is 
too extravagant to be seriously entertained. It would be far more likely that, during 
a naval engagement, a ship should be almost touched by several thousand balls, with- 
out being ever struck by a single one. Moreover, there is not the slightest evidence 
that meteorites ever perform such remarkable feats of precision, or experience so many 
narrow escapes from a collision with the earth; for, instead of being observed depart- 
ing into space, they suddenly disappear after their encounter with the air. The small 
amount of solid matter which falls to the ground on these occasions is justly regarded 
as inadequate to evolve so vast a body of light by acting on the rarefied air at great 
elevations; but our globe seems to be invested with an atmosphere of zther having far 
more wonderful properties. Astronomical investigations prove the existence of a rare 
medium pervading all space; and this subtle fluid cannot be wholly insensible to che- 
mical forces, which alone could render it useful in nature’s economy. Extreme rarity 
would, indeed, prevent it from undergoing any chemical change in the interplanetary 
regions; but it is compressed to a much greater density about the vast spheres by 
which space is tenanted. The atmospheres of this fluid enveloping the earth and the 
other large planets, are not sufficiently dense for chemical action, except in cases 
where they receive an additional pressure from meteoric bodies sweeping through 
them with wonderful rapidity. The evolution of light on such occasions depends, not 
only on the size and velocity of the falling mass, but also on the direction in which it 
approaches the planetary surface; and observation shows that the most brilliant meteors 
move very nearly parallel to the horizon. But around the sun a much stronger attract- 
ive force gives this ethereal fluid the compression necessary for a constant chemical 
action, and a steady development of light; while the realms of space furnish inex- 
haustible supplies of the luciferous matter, and impart perpetual brilliancy to the great 
luminary of our system. It is not possible that the self-luminous condition of the sun 
could be maintained by any combustible, or light-yielding matter ; of which it is com- 
posed. From a comparison of the relative intensity of solar, lunar, and artificial 
light, as determined by Euler and Wollaston, it appears that the rays of the sun have 
an illuminating power equal to that of 14,000 candles, at a distance of one foot; or 
of 3500,000000,000000,000000,000000 candles, at a distance of 95,000,000 miles. 
It follows that the amount of light which flows from the solar orb could be scarcely 
produced by the daily combustion of 700 globes of tallow, each equal to the earth in 
magnitude. A sphere of combustible matter much larger than the sun itself should 
