218 
POPULAR SCIENCE REVIEW. 
ing energy witli which both in theory and practice it has been 
pursued. A zone of small planets has been discovered between 
Mars and Jupiter just where the analogies of the planetary dis- 
tances indicated the probable existence of a large planet. The far- 
off Neptune was revealed in 1846 by a process of analytical rea- 
soning, as unique as it was triumphant, and which proved how 
well the theory of planetary perturbations was understood. The 
planet was discovered by calculation ; its position in the heavens 
assigned, and the telescope was then employed merely as the 
instrument of its detection. The number of satellites which a 
century ago numbered only ten has now reached twenty ; and 
the discovery in 1877 of two moons accompanying Mars shows 
that the work is being continued with marked success. In 
other departments we also find similar evidence of increasing 
knowledge. The periodicity of the Sun-spots, the existence of 
systems of binary stars, meteor showers and their affinity with 
cometary orbits, may be mentioned as among the more important, 
while a host of new comets, chiefly telescopic, have been de- 
tected. Large numbers of nebulae and double stars have been 
catalogued, and we have evidence every year of the activity 
with which these several branches are being followed up. In 
fine, it matters little to what particular department of astro- 
nomical investigation we look for traces of advancement during 
the past hundred years, for it is evident throughout them all, 
and sufficiently proves that the interest formerly taken in the 
science has not only been well sustained, but has become more 
general and popular, and is extending its attractive features to 
all classes of the community. In Herschel’s day, large tele- 
scopes were rare. A man devoting himself to the study of the 
heavenly bodies as a means of intellectual recreation, was con- 
sidered a phenomenon and, indeed, that appellation might be 
fittingly applied to the few isolated individuals who really occu- 
pied themselves in such work. How different is the case now 
that the pleasant ways of science have called so many to her side, 
and so far perfected her means of research as to make them 
accessible to all who care to see and investigate for themselves 
the unique and wonderful truths so easily within reach P Large 
telescopes have become common enough, and there is no lack 
of hands and eyes to utilize them, nor of understanding, ever 
ready to appreciate, in sincerity and humbleness, those objects 
which display in an eminent degree the all- wise conceptions of 
a great Creator ! It is, therefore, a most gratifying sign to 
notice this rapid development of Astronomy, and to see year by 
year the increasing number of its advocates, and the record of 
many new facts gleaned by vigorous observation. 
The character of recent discoveries distinctly intimates that 
in future years some departments of the science will become 
