344 D. Trowbridge on the Nebular Hypothesis. 
sustenance exists. But the fatal objection to this theory, and 
all theories which look to the physical or chemical condition of 
the soil, or even to climatic peculiarities, for an explanation of 
the treeless character of the prairies, is discovered in the fact 
that trees will grow on them when once introduced—not water- ° 
loving trees exclusively, but evergreens, deciduous forest trees, 
and fruit trees—such as flourish in all the arable and habitable 
e 
fact alone militates fatally against the views advanced by Whit- 
ney as well as those of Engelmann, Bourne, Atwater and others, 
who have attributed the distinctive character of the northwestern 
prairies to an excessive humidity of the soil. 
University of Michigan, Aug. 30, 1864. 
Art. XXXIV.—On the Nebular Hypothesis; by DaviD 
TROWBRIDGE, A.M. 
ory of the subject first, and then the phenomena of Nature are 
compared with the theoretical conclusions. 
The only apology which I have to offer for going over 80 
much of the subject is that I attempted to prepare some articles 
on detached portions of the hypothesis, and found the explana- 
tions, which would be necessary to render the subject intelligible 
to those who had not made the matter a study, so many that the 
space demanded would be nearly equal to that occupied by the 
present paper. . 
That there is a growing interest in the subject, is known to 
every astronomer that has paid any attention to what has been 
written. Itisa great problem yet to be completely resolved. 
The complete analytical treatment of the nebular hypothesis 
presents many difficulties; and without such aid it seems impos 
sible to ascend to the origin of the solar system. .I now submit 
what follows to the candid judgment of my readers. 
Compare Wells, this Journal, i, 331, where the forest is said to be encroaching 
8 the pr ri s about St. Louis; En, Ibid., [2], xxx 389; Edwards, Rep- 
et sp vecnie-er-eon reg Eero sana ot Remake 
