156 Meteoric Astronomy. (April, 
The reader has only to turn to Fig. 4 and to conceive 
the meteoric cross sections marked in all over the circular 
space E,E,E,E, with that degree of increasing richness swn- 
wards which has been indicated above (remembering also, 
that as at present drawn, the figure shows less than half 
the real number of cross sections overlapping the earth’s 
orbit), to perceive how richly sun-surrounding space must be 
crowded with meteoric systems. For not the ecliptic plane 
alone, but every plane through the sun, must be similarly 
intersected. 
Albeit we must not forget that the meteor-systems seve- 
rally are almost infinitely tenuous. It has been calculated 
by Professor Newton, of America, that even on the occasion 
of the great display of November meteors in America, in 
1867, the portion of the system actually traversed by the 
earth contained only one meteor in goo,000 cubic miles of 
space: that is, in a cubic space nearly 100 miles long, 
broad, and deep, so that even taking into account the 
greatly increased richness close by the sun, we have not to 
deal with a real crowding of cosmical material ; but, on the 
contrary, with an excessive tenuity, using this word to 
indicate the relation between the quantity of matter (how- 
ever distributed) and the volume of the space within which 
it exists. 
The reader will doubtless have surmised already the 
special purpose which IJ have had in view in the preceding 
inquiry. It seems to me that we have, in meteoric pheno- 
mena, as well as in the associated phenomena of comets, 
the explanation of some at least of the features presented by 
the solar corona. I cannot see how, on the one hand, the 
irregularities of stru¢éture which the corona presents at 
great apparent distances (up to twoor three solar diameters, 
for instance) can be accounted for except by the theory that 
during eclipse the complicated network of meteor systems 
becomes discernible; nor, on the other, how the meteor 
systems can by any possibility escape recognition when a 
total solar eclipse is seen under favourable atmospheric 
conditions. 
It has been supposed that, because I have advocated 
another theory in explanation of other features of the corona, 
I have abandoned the meteoric theory which I had formerly 
advocated. It is true that, in general, to advocate a new 
theory implies that a theory formerly held has been aban- 
doned. But, in the present instance, this is not the case. 
The solar corona is a complicated phenomenon, and presents 
features which are severally due to different causes. Its 
