1874.] Notices of Books. 105 
that, just as the hydrogen line widens as the surface of the sun 
is approached, indicating increase of pressure, so, in the sun- 
spot, the pressure of the incandescent sodium vapour increases 
as we go deeper into the sun-spot cavity. Finally we have an 
account of the velocity of solar storms, calculated from the 
shifting of the F line, to be something like a hundred miles in a 
second. 
Altogether the work is very readable, and it will form a useful 
introduction to larger works, such as that of Roscoe or Schellen. 
It shows, however, frequent evidence of haste, both in style of 
composition and in arrangement of subject-matter, and several 
somewhat abstruse subjects receive rather slight treatment. We 
regret also to notice the comparatively slight mention of foreign 
investigators, and of our own Miller, Brewster, and Herschel. 
But we must bear in mind that the subject is vast, and three 
hours of exposition are very insufficient for a detailed account of 
only one branch of it. We commend the work to all who 
are interested in one of the most prominent branches of optical 
science of our day, and remind them that it is the work of one 
who has done good service to science by his own researches. 
Light Science for Leisure Hours. Second Series. Familiar 
Essays on Scientific Subjects, Natural Phenomena, &c., 
with a Sketch of the Life of Mary Somerville. By Ricuarp 
A. Proctor, B.A., Cambridge, Honorary Secretary of the 
Royal Astronomical Society, &c. London: Longmans, 
Green, and Co. 1873. 
Some years ago a caricature portrait of Alexandre Dumas was 
published in Paris, in which the brilliant novelist was pictured 
with a bunch of hands attached to each arm, and each hand 
carrying a pen that was scribbling furiously. The flood of 
books, magazine articles, controversial and other correspondence, 
besides communications and hard secretary’s work to the Royal 
Astronomical Society, which, during the last few years, have 
poured from the pen of Mr. Proctor, render a similar caricature 
almost justifiable, but it demands some modification. Instead of 
merely a bunch of supplementary hands, the artist would, in this 
case, require to depict an efflorescence of supplementary brains, 
Mr. Proétor’s work having been something considerably beyond 
the efforts of a mere book-maker. He has specially attacked the 
grandest and heaviest of the sciences, and made it the leading 
subject of his popular teaching; but, instead of re-baking the old 
dishes of his predecessors, he has laid before his readers the most 
recently discovered facts, generalisations, and speculations of 
modern astronomy; a large proportion of which, according to 
the old method of dishing up astronomical handbooks, would 
have remained during another generation or so buried in the 
Transactions of learned societies, or in the unread volumes 
VOL. Iv. (N.S.) P 
