1874.] Notices of Books. 529 
once the longest and the most interesting contained in the 
volume: it was originally brought out in ‘The Student” for 
February, March, and April, 1869; therefore many discoveries 
and some extensions of the subject have been made since, but 
this in no way interferes with the correctness of the paper. 
Mr. Proctor begins by a comparison of what was known of the 
solar system at the end of the last century with what is known 
at the present time: first among the remarkable discoveries 
made within the last sixty years must be noticed the great 
increase in the number of primary attendants upon the sun; 
the g8th asteroid was just discovered at the time this Essay was 
written, and yet it was but on the opening day of the present 
century that the first of these bodies was brought to light. The 
mind gets bewildered in imagining all these bodies, primaries of 
the planetary system, revolving in paths closely interwoven, the 
more so when—given these constant additions to the numbers 
known—we may fairly assume that for each discovered asteroid 
there are to be reckoned tens, perhaps hundreds, which will 
never be found out. Then the myriads of dependent comets 
that are found to exist within the solar system, revolving round 
the great centre in the most eccentric orbits, must still remain 
among the mysteries of Science. At the present time, when the 
minds of even the most unscientific among us have been more 
or less interested by the appearance of a comet, this branch of 
the subject presents a special attraction, and it is most ably 
treated. A still more remarkable feature of modern astronomical 
discovery remains to be noticed; that is, that meteors, shooting 
stars, and aérolites, which have always been regarded as meteor- 
ological phenomena, must now be placed among the attendants 
of the sun. It is beyond doubt that the earth encounters 
fifty-six systems at least of these small bodies, and ‘‘ What is 
the likelihood,” asks Mr, Proctor, ‘‘that if there were only a few 
hundreds of such systems the earth would encounter so manyas 
fifty-six?’ ‘The extreme probability, nay certainty, is that such 
systems may be reckoned not by hundreds and thousands, there- 
fore, but by millions of millions. A close connection, if not 
identity, can be traced between comets and shooting star sys- 
tems, as it is discovered that at least two of the meteoric systems 
coincide with the orbits of known comets. The Sidereal System 
next engages the attention, and the last twenty pages of this 
Essay are devoted to the consideration of what our astronomer 
terms ‘“‘those mysteries of mysteries,’ the nebula. The entire 
paper deserves careful and attentive study. 
The next article, bearing the title “‘ What Fills the Star 
Depths?” is almost entirely devoted to mathematical problems 
proving that the arrangements of stars in different regions, &c., 
is not the result of accident, but rather that some real laws of 
aggregation exist among the stars. And then we come to an 
Essay of great interest, headed “ Star-Drift,” and treating—as 
