Nebular Theory. — Mislnclclcs. 311 
representing:^ the Snn. and this slup cunnected by means of a 
cable with another ship of abont ten tons carryinp^ capacity 
representing Jnpiter, and that these two ships wonld ])nll 
witli all their might in opposite directions. We snppose, fnr- 
ther. that to the cable — representing the force of gravity 
— connecting the two ships were fastened small boats of 
from abont 70 to 640 pounds carrying capacity. These 
wonld represent the inner larger planets. We must then 
certainly admit that the cable, with one ship at cither end, 
and the ships pulling with all tlieir ])i)wer in ojjposite direc- 
tions, would represent a straight line, if not influenced by 
some other force, causing a different result. 
Tliose two ships and the small boats, mav be said to be 
in conjunction; and such a position is sometimes occupied 
by all the planets simultaneously This happens \'ery sel- 
dom, however, but sometimes it does happen. Jupiter, Ura- 
nus and Xeptune formed about a straight line with the Sun 
in 1881-82, whereby the inner planets in crossing this line 
were also placed in the same conjunction. The tension is, 
of course, greatest during such epochs ; but Jupiter alone w'ill, 
as shown in the example above, hold the orbits of the inner 
planets in the ecliptic or about identical with its own orbit, 
when they coine between him and the Sun once in each 
anomalistic period. When we, further, notice that Xeptune 
at a distance of 1,000 million miles exerts a disturbing in- 
fluence on Uranus, which observations have convinced us 
of, then we may safely consider it established beyond all 
doubt, that the positions and relations of the planetary or- 
bits as determined are fixed and unchangeable by the recip- 
rocal attractions of the Sun and the planets. All this is, 
indeed, simple and natural. And thus we understand that 
we can explain these phenomena without supposing, as the 
cosmologists have done, the existence of a nebula with a 
diameter of over 5,000 million miles, in order to make it 
explicable. 
It is equally clear, that the moons are subject to the same 
kind of attractions, since they frequently are in conjunction 
not only with the Sun, but also with each other. The inner 
moon of Mars, for instance, comes between the Sun and the 
planet three times a day. It appears plain, therefore, that 
