NATURE 
309 
THURSDAY, FEBRUARY 1, 1883 
POPULAR ASTRONOMY 
The Sun, its Planets, and their Satellites. A Course of 
Lectures upon the Solar System, read in Gresham 
College, London, in the Years 1881 and 1882. By 
Edmund Ledger, M.A., Rector of Barham, Suffolk. 
Pp. 432. (London: Stanford, 1882.) 
NOTHER work on Astronomy! It must have 
demanded some courage to venture on such an 
attempt in these days, so unprecedentedly fertile in 
similar undertakings. We are not speaking of the inun- 
dation of lighter productions—the magazines, the lectures, 
the newspaper articles—by which the lower grounds of 
modern society are overrun, to the benefit no doubt, in 
many cases, of those who may thus be led to find out in 
what a glorious world they live. Provided only that such 
efforts have something clear and something pleasant 
about them, we shall not be disposed to say “the fewer 
the better cheer.’”’ It is a worthy and honourable attempt, 
to introduce one new interest, one fresh and innocent 
pleasure, into the dull round of a careworn plodding life. 
The shepherd will love his work none the less for learning 
something of the movements of his “ unfolding star :” the 
evening of the weary mechanic will bring unalloyed re- 
freshment, if he is enabled to turn an inquiring gaze 
upon “‘the fields of light that lie around the throne of 
Gop.” But not only is provision being thus made for the 
development of thought and intelligence among those 
whose lives too often are divided between uninteresting 
labour and debasing gratification, but a corresponding 
advance has been made in the production of treatises 
addressed to the possessors of more cultivated minds and 
leisurely opportunities. A full collection of such treatises 
during the last half-century would be at once voluminous 
and interesting. What would come out in strong relief 
from a comparison of them would be the comprehensive- 
ness and many-sidedness of the subject. It is indeed a 
glorious subject—the ‘consideration of the heavens”; 
the subject of a life-time, of many life-times—in all its 
complexity of magnificence. No one mind, no one book, 
can do it justice. It is as boundless as the spaces of 
which it treats, and the mechanism which it professes to 
explain. [t embraces no small part of the history of 
human intelligence ; it demands the utmost power and 
subtlety of the most consummate analysis ; the picturings 
of the most poetical imagination will be tame and feeble 
in the presence of its realities ; and yet so simple are 
many of its elementary truths as to invite and recompense 
familiar inquiry. There may be room then for another, 
and another, and yet another work on astronomy ; and 
provided they are thoughtfully designed and accurately 
wrought out, there will be little question as to their suc- 
cess ; for it arises from the very comprehensiveness of 
the matter, that every writer will address himself to the 
task from his own point of view, and all readers may find 
something to interest them in every varied presentation 
of the subject. 
We are pleased to give a welcome reception to the 
treatise which is now before us. In many respects it will 
be found worthy to take rank among the best. Where, 
VOL. XXvVII.—No. 692 
as we have said, the study is so many-sided, it is obviously 
better to work on certain lines ; not to attempt too wide 
a grasp, with the inevitable annoyance of bulk and cost- 
liness ; not to be led into the opposite course of saying a 
little about everything, and enough about nothing. The 
author of these Lectures has chosen his own line, pre- 
ferring to give us a good deal that is explanatory of the 
mechanism of the solar system, and a good deal that is 
descriptive of its wonders. And he has executed his task 
on the whole remarkably well. He has evidently a clear 
apprehension of what he is going to write about, and 
therefore succeeds in mak ng it clear to other minds ; 
and there is a pleasant facility in his style which imparts 
readableness to matters intrinsically somewhat dry. And 
if we meet with little of vivid and imaginative description, 
its place is supplied by a truly valuable amount of caution 
and discretion in dealing with the theories of the day. If 
he does not lead us far he will certainly not lead us wrong: 
and ‘‘ when,” as he characteristically tells us, ‘we know 
so little, we must not let our ignorance suggest unnecessary 
difficulties. Rather let it teach us to wait, and watch, 
and learn.” Availing himself of no common extent of 
reading, he has used his materials with conscientious 
accuracy; and if we may venture to point out a few 
matters to which in our view some exception might be 
taken, we hope it may be looked upon as only the fulfil- 
ment of his own express desire to receive friendly com- 
munications of this nature. 
A comparatively undeveloped point, we venture to 
think, in the programme, is the very brief notice that has 
been taken of the theory of the tides. Granted that its 
minuter details are affected by some complicated con- 
siderations, its general outline admits of easy explanation, 
and is at the same time the cause of occasional miscon- 
ceptions which ought to be removed ; and it would be 
probably considered by many persons an improvement if 
the larger space allotted to it were obtained at the ex- 
pense of the refutation of the fallacy of the exploded 
Ptolemaic system, 
We do not meet with any reference to outbursts 
of light on the surface of the sun; so interesting a 
proving that the brilliancy of the photosphere may be far 
outshone, and so suggestive as to their possible origin. 
The author’s usual lucidity is scarcely exemplified in 
the explanation of phases in p. 63, ae we venture to 
think a more familiar treatment might have been adopted- 
The larger map by Beer and Madler, notwithstanding 
its able reduction by Neison, might have found place in 
the enumeration of aids to selenographical study. 
There seems a little confusion on p. 77 between Sir W. 
Herschel’s idea that Aristarchus and some other spots 
visible in the earthshine were volcanoes in actual eruption, 
and the observations by Schréter and others of minute 
illuminations on the dark side, which sec.:ned to point to 
an unreflected origin, and are still, unlike the former, not 
accounted for. 
With regard to Mercury, we feel it right to say that Sir 
W. Herschel’s failure’ fo confirm the statements ot 
Schréter may not be entitled to much weight ; as is suffi- 
ciently indicated by their controversy in the PAz/. Trans. 
respecting the phenomena of Venus. As far as this 
latter planet is concerned, it may be concluded, without 
accepting the measures of Schréter, that the irregularities 
P 
