Xcbular Theory. — Mislocklcs. 313 
extent of the oscillation being* 22'. The maxima and minima 
of this oscillation, in general, are not the subject of consid- 
eration in this treatise. 'We jiroposc, however, to discuss a 
peculiarity concerning this oscillation, which hitherto seems 
to have escaped t!ie attention of astronomers. The fact is, 
that the oscillali- n of the lunar orbit is. itself, subject to a 
periodical variation, a variation which stands in harmony 
with the oscillating activity of the Sun. Wy demonstrating 
what the cause of this periodical variation is we shall also, 
thereby, have proven what causes the entire inclination of 
the lunar orbit to the ecliptic. 
It seems, at first glance, quite natural that this character- 
istic of the oscillation which we shall jircsentlv consider is 
due to the Sun's light, since it appears as a result of the va- 
riation of its energy. 
Let us therefore, briefly consider the light and the Sun's 
varying activity during a given time, and then compare the 
results with the oscillations of the lunar orbit during^ the 
same period. 
It is a known fact, that an object facing the Sun, dams 
up the light. We know, further, that the solar rays fall with 
greater strength when they strike an olijcct perpendicularly 
than when they strike it horizontally. The result of this is 
the much higher temperature at the equator than at the poles. 
Thus we understand that as an object dams up the sunlight 
on the Earth's surface, in like manner does the- Earth dam 
up the sunlight in space. The torrid zone becomes the mid- 
dle line in this light-belt, which, thus, lies in the ecliptic and 
diminishes in density as the distance from this line increases 
on either side. When we remember, further, that light is 
electro-magnetic, and as such has a tendency to make the 
ether active wherever it is dammed up. we can no longer 
fail to see that a layer of light-atoms or active ether sur- 
rounds the Earth in the ecliptic and very likely reaches a 
distance beyond the orbit of the moon. 
This ether, thus acted upon, is ditTerent from etli^er in 
general, not only as vibrating and active, but also as offer- 
ing a resisting force. It seems, then, that it is on account 
of this that the moon crosses this zone and inclines to the 
ecliptic, since the resistance met there decreases towards 
