Let them turn aside for a moment from the nebulæ 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 perhaps, was
too short to give us direct evidence of any distinct stages of so
august a process, still the probability was great that the nebular
hypothesis, especially in the more precise form given to it by Roche,
did represent broadly, notwithstanding some difficulties, the
succession of events through which the sun and planets had passed.
[Illustration: DR. WILLIAM HUGGINS, D.C.L., LL.D., PRESIDENT OF THE
BRITISH ASSOCIATION.
Dr. Huggins is one of the most eminent astronomers of the present day,
and his spectroscopic researches on the celestial bodies have had the
most important results. He is a D.C.L. of Oxford, LL.D. of Cambridge,
and Ph.D of Leyden. Dr. Huggins was born in 1824 and educated at the
City of London School. He continued his studies, giving much of his
time to experiments in natural philosophy and physical science. In
1855 Dr. Huggins erected a private observatory at his residence on
Tulse Hill, where he has carried out valuable prismatic researches
with the spectroscope.--_Daily Graphic._]