s 
Recent contributions to Astro-Meteorology. 297 
that the matter which has fallen from the sky is a fragment of that 
of which the stellar universe is formed. And as in such matter there is 
no chemical element that is not found upon the earth, the ‘oiigiioaity of 
composition of all the vie bodies in the universe, ‘alrea dered 
probable by researches with the spectroscope, acquires a new argument 
for its credibility.” 
The further question is then broached, whether it is necessar 
for the original cloud to be made up of such small elements; 
whether, for example, it may not consist of a moderate number 
of comets. In such a case, we ought to meet, from time to time, 
with orbits somewhat unlike, which intersect each other in the 
depths of space, but which lose the characteristics of a common 
system, owing to considerable intervals between the times of 
perihelion passage. 
The question is not anew one. Prof. Hoek of Utrecht has 
found several double gad triple systems of comets,* which ata 
remote epoch were near each other in ea although their peri- 
helion passages nase Gores by years. The most notable of 
their ga maximum Fine e was 1° 33’. Hoek believes 
that the comets of 1677, and of 1683, belong also to this system. 
The antecedent probability of a chance coincidence like that of 
these comets is exceedingly small. 
e find thus analogies baiienen the systems of selpein stars, 
and systems of comets. Can we not imagine mixed systems, in 
which a cloud of meteoroids are grouped i in space ig inion one or 
more larger nuclei, that is, about one or more comets 
If a system of this kind is drawn from solar attraction into 
the figure of a parabolic current, the parabola described by the 
principal body (or those described by the principal bodies) 
should evidently differ very little from the line along the center 
of the parabolic stream, consequently the preceding question is 
answered affirmatively whenever we find a meteoric current form- 
dently form part of _ arto and be one of its elements. 
and the time of crossing g the center of the sone in ta 1866 to. be ) 
Aug. 10°75. With these elements are placed those of the 
1862 III, according to the latest determination of Dr. Oppolzer.t 
_ * Monthly Notices, xxv, 243, and xxvi, 1 and 204. + Astr. Nach, No, 1384. 
