394, REPORT—1868. 
clude that the real average velocity of shooting-stars in their native orbits 
round the sun is not far (1-447) from that of comets moving in parabolic 
orbits, which is greater than the earth’s mean orbital velocity at the same 
distance from the sun in the proportion of 1:414:1. 
In the second letter the origin of meteoric currents is discussed, of which 
more than fifty can be traced which have their points of radiation in the 
northern hemisphere, and it is shown, by their various inclinations to the 
ecliptic, and occasional retrograde motions, that shower-meteors rather re- 
semble comets than planetary bodies indigenous to the solar system. Should 
the meteoric groups come to the sun from stellar space, then, since the 
August meteors have been frequently observed since the date of their first 
recorded appearance, in the year a.p. 830, they must compose streams of enor- 
mous length. Supposing a cosmical cloud of meteoric bodies, of the sun’s 
size, to be moving in space transversely to its distance of, say, 20,000 times 
the earth’s distance from the sun, with a velocity relatively to the sun of 100 
yards per minute, in its approach to the sun it would pass near enough to 
encounter the earth, and its orbit could not then be distinguished from a 
parabola. It will be deformed in its course into a parabolic stream, requiring 
four months and a half to pass through its perihelion. At the middle of 
that time its depth at that point will be only 100 yards, its width twenty- 
three miles, and its density 400 million times its original density, while its 
two extremities will reach in both directions almost up to the orbit of the 
earth. A nebula subtending, under the same initial circumstances as the last, 
1' of arc would occupy more than 225 years in passing through its perihelion. 
Its depth would then be 36, and its width 13,800 miles. Its density would 
be increased in the same proportion as before ; and its length along the para- 
bolic orbit would reach, on both sides, four times the distance of Neptune from 
the sun. If the apparent diameter of the nebula were at first equal to that 
of the sun, it would occupy seven thousand years in passing through its 
perihelion. In this way meteoric currents, enduring, like that of August, for 
hundreds or even for thousands of years can be‘accounted for, whether their 
motion may be direct or retrograde, or at whatever obliquities they are in- 
clined to the ecliptic. 
In the third letter the origin of the November meteors is considered, and 
a summary is given of the new theory of shooting-stars. 
From the known weight of aérolites, and.the absence of any solid residues 
on the occurrence of even the greatest star-showers, the small mass of shoot- 
ing-stars may be certainly inferred. The grains of olivine disseminated in 
meteorites, regarded by M. Daubrée as forming a kind of ‘ universal scoria” 
(see post), may not impossibly compose their nuclei, whose weight, at the 
most, can rarely exceed a few grains. At the earth’s distance from the sun 
a swarm of such particles a few feet apart would be broken up by the sun’s 
attraction into a stream in which each particle would pursue an independent 
orbit. Even in the densest meteoric showers the meteoric bodies are some 
scores of miles asunder, corresponding to thousands of miles apart in the 
distant nebula. The sun’s attraction must, accordingly, gradually deform 
all meteor-clouds circulating within the solar system into a continuous 
stream or closed ving; and, on this account, the November star-shower is a 
recent group, derived from regions beyond the solar system. 
: The new theory of shooting-stars is contained in the following proposi- 
lons :— 
«I. Matter exists in space in every degree of subdivision. Masses of the 
first class are isolated stars, or stars collected together in groups. Those of 
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