PROCEEDINGS 
/'^''yy''''' ^'^ OF THE ~\ 
N ATION/^4^^ADEMY OF SCIENCES 
Volume 2 \ . JANUARY 15, \9W Number I 
A POSSIBLE ORIGIN FOR SOME SPIRAL NEBULAE 
By George F. Becker 
UNITED STATES GEOLOGICAL SURVEY. WASHINGTON 
Read before the Academy, November 17, 1915. Received, November 22, 1915 
In speculations on the evolution of nebulae it has become the fashion 
to postulate an initial spheroid consisting exclusively of elastic fluids, 
this assumption lending itself most readily to exact reasoning and 
computation. 
Kant, Herschel, and Laplace, however, did not assume gaseous 
nebulae. In a paper on Kant as a natural philosopher, printed in 1898, 
I gave an outline of his hypothesis including the following passage:^ 
Tendencies to motions in all directions, excepting in one resultant plane, 
are suppressed by mutual interferences of the free particles. Most of the 
material accumulates at the center, in the sun, but a wide, thin disc of hetero- 
geneous matter remains. This disc consists of discrete particles each of which 
has acquired such a velocity and direction as to maintain the appropriate 
orbital motion Mutual attraction and adhesion, beginning at 
relatively massive particles, cause the agglomeration of the particles in any 
zone or ring to single planets or to groups of planetary bodies. 
From this and other passages it appears that to this very original 
thinker soHd particles were the most essential components of nebulae. 
William Herschel's nebular h3^othesis was founded upon induction 
and observations. Nowhere in his own works do I find so graphic a 
resume as the following which Laplace gave in the Systeme du Monde:^ 
Herschel, while observing the nebulae by means of his powerful telescopes 
has followed the progress of their condensation, not in a single one, for this 
progress could not become sensible to us until centuries had passed, but in 
the aggregate; as in a vast forest one traces the growth of the trees among the 
individuals of diverse ages which it contains. He first observed nebulous 
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