1872.] Meteoric A stronomy. 157 
irregularities may reasonably be attributed to one cause, 
while such features as the straight radial extensions, rifts, 
and so on may be (or rather must be) ascribed to another. 
It may be compared, in this sense, with the aurora. In ex- 
plaining the general nature of this phenomenon, we may call 
into our aid the meteoric particles continually descending, 
in an irregular manner, through the upper regions of 
air; but in accounting for the auroral streamers, we have to 
consider processes taking place along straight (possibly 
along radial) lines. 
It has been objected to the meteoric explanation, that the 
parts of the corona near the sun do not present the appear- 
ance which we should expect to recognise in meteors close 
by the sun, and are furthermore much brighter than we 
could expect even the innermost parts of the meteor region 
to appear. In this reasoning the circumstance seems to be 
overlooked that the meteor light which seems to come from 
regions close by the sun (assuming the meteoric theory to 
be true) does not come wholly, nor even chiefly, from 
meteors really so close to the solar orb. We look through 
a range of meteors two or three hundred millions of miles 
deep (taking into account space beyond the earth’s orbit), 
and it is the combined effect of the light coming from the 
whole of this enormous range that we really recognise,— 
not in the corona, but in that proportion of the coronal light 
which is due to sun-illuminated meteors. The part of the 
range nearest to the sun may be the part most densely 
crowded and most brilliantly illuminated; but its extent is 
limited compared with that of the whole range; moreover, 
the meteors there situated turn but half discs (of reflected 
light) towards the earth, those beyond showing a much 
larger proportion of their illuminated halves. It is worthy 
of notice, indeed, that the farther half of the range supplies 
much the largest proportion of the light, on account of the 
greater fulness of illumination,—for in such a case as this, 
distance per se is an element which may be absolutely 
neglected.* 
It need scarcely be pointed out that the spectroscope 
affords the best means for testing this question. If any con- 
siderable proportion of the corona’s light is reflected from 
* This at first sight may sound paradoxical; but it is stri@ly true neverthe- 
less. The question is one of the apparent brightness of certain regions of the 
heavens, not of the total quantity of light received from given groups of 
meteors. A group of bright objects so far off as to appear like a cloud 
would preserve its brightness absolutely unchanged however far off the 
observer might remove. Its extent alone would diminish. 
