OBSERVATIONS OF LUMINOUS METEORS, 275 
answering to distances of 203 and 57 miles respectively from the meteor’s 
bursting-place, the observations at about twenty stations are on the whole 
in perfect accordance with the supposition that the detonations and audible 
reports of the meteor’s explosion all proceeded from the same point as that’ 
of the termination of the meteor’s course. If four exceptionally discordant 
accounts are retained in the average, it appears as the result that the average 
calculated interval of 2™ 12° for the whole list of stations is exceeded by the 
average of the observations themselves by 18 seconds, or by about 10 per 
cent. of the real value ; this would easily be accounted for by the long duration 
(in some cases about 1™) of the thunder-like echoes of the sound, to develop 
and prolong which mountainous localities would be particularly favourable: 
but if these four very discordant observations (all near the end point of the 
meteor’s course) are omitted, the remaining seventeen observations exhibit 
no such retardation, and the average observed time-interval is identical with 
that found by calculation of the observers’ distances from the end point of 
the meteor’s course. 
The most important conclusion established by Dr. Galle’s calculations is 
one which Prof. v. Niessl had already demonstrated independently, that the 
orbit of the meteor-mass composing this fireball round the sun was neither 
an ellipse nor a parabola, but an hyperbola. On entering into collision with 
the earth’s atmosphere and traversing its outer layers as shooting-stars and 
fireballs, meteor grains and masses present different directions of motion 
from those which they may be shown, by a proper treatment of the obser- 
vations, to have had originally in their orbits. The causes of this difference 
are of various kinds, some evident and considerable, and others for the most 
part insensible in their effects; but tables have been given by Professor 
Schiaparelli for obtaining a meteor’s real radiant-point in its orbit from that 
presented by observers’ descriptions of its apparent or atmospheric path, 
whenever the latter is known exactly, and when the meteor’s velocity is also 
considered to be certainly determined. In such cases every influencing cir- 
cumstance can be allowed for, whether it is the earth’s own rapid motion in its 
orbit, and its far less rapid rotation (especially in moderately high latitudes) 
about its axis, making the meteor’s motion as observed only relative to the 
earth’s centre (or surface when extreme accuracy is desired) instead of to 
the sun and fixed stars, to whose sphere alone, before its collision with the 
earth, the cosmical path of the meteorite properly belongs; or whether it be 
the earth’s attraction causing the meteor to dip or descend more steeply as it 
approaches, and at last plunges obliquely into the atmospheric ocean, As a 
rifle-bullet fired horizontally over a level plain will strike it more and more 
perpendicularly the less the force of the charge and the speed of the projectile 
is made, so Prof. Schiaparelli shows that by the accumulated attraction of 
the earth upon it (until it enters the atmosphere and is finally arrested) an 
ordinary meteorite* overtaking the earth with the least possible relative 
speed that it can have, and grazing the earth’s atmosphere horizontally at 
last, will have its apparent radiant-point raised 17° by “ zenithal attraction,” 
which is the name by which he has distinguished this correction. If the 
same meteorite moved from the opposite direction, meeting the earth instead 
of overtaking it, and at last grazing the atmosphere horizontally, the zeni- 
thal attraction of its apparent radiant-point would be less than half a degree, 
or about 0° 20’. The actual speeds of these two meteors’ flights through the 
* Meteoric bodies with hyperbolic or nearly circular paths (if such exist) are here ex- 
cepted, and only those are considered, forming prebably far the most numerous class, 
whose orbits are parabolas or very long ellipses. 5 
re 
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