s of nebulae up to that time were really in favor
of an evolutional progress. In 1864 he (the speaker) brought the
spectroscope to bear upon them; the bright lines which flashed upon
the eye showed the source of the light to be glowing gas, and so
restored these bodies to what is probably their true place, as an
early stage of sidereal life. At that early time our knowledge of
stellar spectra was small. For this reason partly, and probably also
under the undue influence of theological opinions then widely
prevalent, he unwisely wrote in his original paper in 1864, that "in
these objects we no longer have to do with a special modification of
our own type of sun, but find ourselves in presence of objects
possessing a distinct and peculiar plan of structure." Two years
later, however, in a lecture before this association, he took a truer
position. "Our views of the universe," he said, "are undergoing
important changes; let us wait for more facts with minds unfettered by
any dogmatic theory, and, therefore, free to receive the teaching,
whatever it may be, of new observations."

THE NEBULAR HYPOTHESIS.

Let them turn aside for a moment from the nebulae in the sky to the
conclusions to which philosophers had been irresistibly led by a
consideration of the features of the solar system. We had before us in
the sun and planets obviously not a haphazard aggregation of bodies,
but a system resting upon a multitude of relations pointing to a
common physical cause. From these considerations Kant and Laplace
formulated the nebular hypothesis, resting it on gravitation alone,
for at that time the science of the conservation of energy was
practically unknown. These philosophers showed how, on the supposition
that the space now occupied by the solar system was once filled by a
vaporous mass, the formation of the sun and planets could be
reasonably accounted for. By a totally different method of reasoning,
modern science traced the solar system backward step by step to a
similar state of things at the beginning. According to Helmholtz, the
sun's heat was maintained by the contraction of his mass, at the rate
of about 220 feet a year. Whether at the present time the sun was
getting hotter or colder we did not certainly know. We could reason
back to the time when the sun was sufficiently expanded to fill the
whole space occupied by the solar system, and was reduced to a great
glowing nebula. Though man's life, the life of the race per