408 REPORT—1868. 
the 6th of December 1798, of which no former record appears to be pre- 
served, must rather have been temporarily, and, in the latter case, recently 
introduced into the solar system from without. 
The real form and extent, and the mode of the production, of meteoric 
rings would thus remain uncertain, if the recent discovery of their affinity 
with periodic comets had not to some extent revealed their history, and 
removed, at length, one chief obscurity from the theory of meteor rigs— 
that is to say, their frequent retrograde motions, and great obliquities to the 
ecliptic, of which the nebular hypothesis of Laplace, when it is attempted 
to be applied to explain their origin, can give no account. 
The two principal meteoric showers, of August and November, and pro- 
bably also those of April and December, having been recently identified in 
their orbits with the orbits of certain periodic comets, one of which performs 
its revolution, with a periodic time of upwards of 400 years, in an orbit ex- 
tending, at its greatest distance, twice as far as the furthest planet, Neptune, 
from the sun, the community of origin of comets and shower-meteors, at 
first suspected, now appears to be finally established. It is stated in the first 
chapter of Professor Schiaparelli’s memoir as the new astronomical theory of 
luminous meteors, about to be further developed and applied to the explana- 
tion of their phenomena. 
In the second and third chapters some points of the theory of the atmo- 
spherical origin of meteors are regarded as requiring special consideration and 
discussion. Deviations from uniform motion, such as crooked paths * and 
changes of velocity, regarded by M. Coulvier-Gravier as the effects of violent 
air-currents, are shown to arise from the resistance of the air to the original 
motion of the meteors. The diurnal variation of frequency, noticed by M. 
Coulvier Gravier, and the similar annual variation, also observed by him, by 
Dr. Schmidt, Dr. Wolf, and by others, together with the variations of the 
average direction of meteors throughout the day, or year, are shown to have 
no direct connexion with meteorological changes, but to correspond to the 
varying altitude and azimuth of the apex of the earth’s way, from which the 
greater number of meteors are directed. 
Formule for calculating the amount of these periodical variations led Prof. 
Schiaparelli, in his first letter to Father Secchi, to regard the real velocity of 
meteors as identical with that of bodies revolving in parabolic orbits round 
the sun. They were similarly investigated and employed by Professor 
Newton in pointing out the resemblance of the orbits of shooting-stars to 
those of comets. A popular account of the phenomena of meteoric variations 
is given at the conclusion of the chapter, by supposing a ‘‘ meteoric sun,” or 
central radiant-point of shooting-stars, to be situated at the apex of the 
earth’s way—whose rising and setting produce a meteoric morning and 
evening, and its culminations a meteoric noon and night, siw hours before the 
corresponding changes of the sun. A meteoric spring and autumn, summer 
and winter are a consequence of the varying declination (or meridian altitude) 
of the same “meteoric sun,” and accordingly follow three months after the 
corresponding tropical seasons of the year. 
* Of meteors with decidedly crooked paths, M. Coulvier-Gravier reckons that about three 
such meteors are visible in every thousand. Meteors with decidedly serpentine flights were 
only observed by him three or four times in the course of many years. M. Schiaparelli 
further suggests that the helix, or spiral curve in which small strips of card, 2 inches long 
and 4 inch wide, descend through the air when let fall from a height, combined with the 
foreshortening and exaggerating effects of perspective, faithfully represents all the peculiari- 
ties of curyed and retarded flight occasionally observed in shooting-stars. 
