23: RESULTS OF RECENT RESEARCHES ON THE 
a nebula is not very heterogeneous, and hence in general the foregoing conclusions would 
not be greatly modified. In this reasoning I have assumed nothing but that the nebule 
are figures of equilibrium under the action of gravitation. That these masses are fluid 
is certain, for the bright lines of their spectra indicate that they are self-luminous gas ; on 
the other hand the same force which controls the motions of the stars must operate 
among the particles of the nebule, and thus determine the figures of the masses in accord- 
ance with the laws of mechanics. 
As the conditions here assumed certainly exist in the heavens, we need only add 
that when the masses separate they are probably revolving as a rigid system. When 
they contract under the influence of gravitation, they must by a well-known mechanical 
law gain in velocity of axial rotation, and tidal friction then begins expanding and 
elongating the orbits; in the course of some millions of years we have a double star like 
a Centauri or 70 Ophiuchi. 
The stellar cosmogony here suggested may be regarded as a very general theory. 
Our solar system is so remarkable, that it is uncertain whether a theory which explains 
the formation of double stars could assign also the cosmogonic processes which have given 
birth to the planets and satellites. The masses of the planets are very small compared to 
that of the sun, and the masses of the satellites are equally insignificant compared to 
those of the planets about which they revolve. Moreover the orbits are very circular, 
and these various circumstances make our system absolutely unique in the known crea- 
tion. Yet so far as our researches on the double stars may illuminate the problem of 
planetary cosmogony, they indicate that the separation took place in the form of lumpy 
or globular masses—not in rings or broad zones of vapor such as Laplace supposed. 
From the survey thus hastily made of a very large subject, it appears that we have 
taken a step in the generalization of the theory of tides and of tidal friction, and have 
indicated the probable mode of formation of the stellar systems. Little or nothing 1s 
known of the development or even of the mechanism of star clusters; the problem of 
explaining the more complicated systems must ultimately occupy the attention of 
astronomers if we are ever to trace the development of the visible universe. As a step 
in the direction of accounting for the origin of multiple systems, it may be said that 
observations on triple and quadruple stars have shown that they, too, developed by repeti- 
tion of the fission process. One or both components of a binary have again subdivided, 
just as I inferred was the case when still at the Missouri State University in 1888. While 
the views here expressed are the results at which I have arrived after a partial investiga- 
tion of the theory of tides and of the figures of equilibrium of rotating masses of fluid 
and a comparison of these theories with the phenomena observed in the heavens, I 
reserve the right to modify any opinion or conclusion which future research may show 
