132 
Notices of Books, [January, 
Mr. ProCtor’s mathematical attainments have not deprived him 
of the use of unsophisticated language and argument ; he can 
reason as well as formulate ; he does not use mathematical ex- 
pressions as a substitute for descriptive reasoning, but only when 
they are actually demanded by the essentially mathematical 
nature of his subject. Even then he uses the simplest forms, 
such as most ordinary readers can follow with a slight effort of 
attention. 
The first chapter of this book, dealing with the stricftly mathe- 
matical subject of the sun’s distance and dimensions, is a notable 
example of this admirable characteristic of Mr. ProCtor’s disser- 
tations ; and similar powers of elucidation are displayed in the 
third chapter, on analysing sunlight, We know not where else 
the unlearned reader could find an equally profound yet clear 
and simple treatment of these subjects. 
The interest of the later chapters is considerably enhanced by 
the author’s free handling of the theoretical elements of the 
subjects. Scientific writers of the patronising school are too 
apt to assume that debatable hypotheses are above the reach of 
the populace whom they condescend to instruct. Mr. ProCtor 
evidently proceeds on almost an opposite principle, and treats 
his readers with quite a banquet of speculative viands, leaving 
them to choose those that are the most agreeable to their own 
intellectual palates. This adds greatly to the interest of his 
books. Many who would fall asleep over a detail of bare phy- 
sical faCts and quantities are kept awake by the discussion of 
contending hypotheses, and faCts which would otherwise slip 
from their memory are fixed there by their necessary association 
with an exciting controversy. 
The absence of a full index is a sad defeCt in this book. The 
table of contents is good enough, fuller than usual, but this can 
never supersede the necessity for an alphabetical index to every 
standard work that is to be used for the purpose of obtaining 
solid information. 
It may be that Mr. ProCtor is a bad index maker, or too busy 
to attend to this mechanical department of authorship. If so, 
he would do well to call in the help of a friend who has the 
faculty of index-making. It is by no means necessary that the 
author should make his own index. The best index extant is 
that which was made by the late Robert Cox, of Edinburgh, for 
the “ Encyclopaedia Britannica and the next best with which 
we are acquainted is that appended to his own work on “ Sabbath 
Laws and Sabbath Duties,” a pamphlet of 16 pages with 547 pages 
of Appendix; the pamphlet in pica , the Appendix in small pica , 
and the voluminous notes to the Appendix in very close brevier » 
