On Meteorites. 107 
orbit designated by this date is intersected by the orbit of the 
meteorite. It now often happens that the earth is struck by meteorites 
on the same date during two or several consecutive years. This can 
only be explained by the earth on that date passing through a swarm of 
meteorites, or, rather, through a long stream taking several years 
in passing—if we consider that, on an average, no more than four 
falls of meteorites are recorded yearly. Thus, the earth was hit 
four times by meteorites on the 13th of December, between the 
years 1795 and 1813.! Since then the earth has not collided with 
any meteorites on that date. 
Still more remarkable than dates which, like the above, show 
the meteorites to go in flocks, are others from which, with a con- 
siderable degree of probability, we may infer a certain period. Thus, 
the 13th of October is a date worth mentioning, as on that day falls 
of meteorites occurred in 1787, 1819, 1838, 1852 and 1872. On 
examining the differences between these years, they will be found 
to be very nearly multiples of 6}—viz.: 5x6}, 3x6} and 2x6}. 
These falls, consequently, seem to belong to the same flock, with a 
period of between six and seven years. The flock must be rather 
lengthened and takes a considerable time to pass, since the earth 
passes it so often, as is recorded in this case. If the stream be short, 
there is, of course, very little change of the earth being just in the 
point in which the orbits of the earth and the meteorites cross eac 
other every time the stream is passing. This would only be the 
case if the period were exactly one or more whole years. As this, 
of course, occurs but very seldom, it is not to be expected that the 
differences between the years be exactly multiples of the periods. 
It may be well to quote other similar periods of meteorites. In 
February, two series of falls are particularly notable, viz. :— 
February 19, 1785, at Witmess, February 19, 1796, at Tasquinha. 
n 18, 1815, at Duralla. ef 18, 1824, at Irkutsk. 
= 16, 1876, at Indesgherry. a 16, 1883, at Alfianella. 
The possibility here suggests itself that the earth on February 
19, 1785, met a flock of meteorites which, with a period of about 
thirty years, reappeared in 1815. No fall is on record from the 
next meeting. From the one then to follow, however—that is, 
from the one to take place sixty-one years from 1815—viz., in 1876, 
a fall is recorded. It will be observed that the dates are receding, 
‘To these falls may be added a fifth, which occurred on the Western 
Hemisphere, December 14, 1807. 
