246 NATURE 
and the author has succeeded in bringing together 
a mass of useful information and presenting it in 
an interesting form to the reader. A valuable 
feature in so new a subject is that full references 
are given for all the data, and at the end there 
is a bibliography. Hee pee Re 
MATTER AND THE STRUCTURE OF THE 
ETHER. 
The Universe and the Atom. By M. Erwin. Pp. 
314. (London: Constable and Co., Ltd., 1915.) 
Price 8s. 6d. net. 
ae work is divided into two parts, the first 
being devoted to a general discussion of 
wave motion, and the second to a special theory 
as to the structure of the ether and its conse- 
quences. The theory called ‘‘the pan-cycle hypo- 
thesis” deals with “invisible composition light 
waves, the warp and woof of the ether structure 
and of all things material.” 
In spite of some inaccuracies, the first part con- 
tains quite an interesting account of the nature of 
wave motion, although the long and frequent 
quotations from other text-books make the style 
somewhat disjointed. In some places too much 
stress is laid on the obvious, which indeed at times 
is so over-elaborated as to lead to absurdities. It 
is worth quoting one such passage, for the deduc- 
tions drawn are used later to explain the theory 
of the mechanical structure of the ether. ‘Thus 
if a force of 5 units is operating in one direc- 
tion, dnd another force of 3 units is operating on 
the same particle in the opposite direction, we say 
they are equivalent to a force of 5 - 3=2 units of 
force operating in the first direction. We mean 
by that the particle would move from its first 
position, in the direction impelled by the greater 
force, and behave as if it were acted on only by a 
force of 2 units. This is all that composition of 
force gives us, but it does not speak the full event. 
It makes 3 of the greater units of force annihilate 
the 3 units of force operating in the opposite 
direction. Now force represents energy, and 
energy is never destroyed” (p. 74). i 
The second part deals with a new theory of 
ether structure, the nature of electrons, atomic 
theories, gravitation, and other fundamental ques- 
tions based on a conception of the ether organised 
by so-called ‘force rays” resulting from trains 
of waves proceeding in different directions through 
the ether and producing stationary waves. The 
ideas involved do not seem very helpful in throw- 
ing light on these fundamental questions, and in 
many cases there is a marked lack of adequate 
discussion of existing theories. Thus the modern 
attempts to explain the Balmer series is dismissed 
with the following short paragraph :—‘ This for- 
mula by Balmer was derived entirely by trial from 
the observed wave lengths of the first fifteen lines 
of the hydrogen series. It has so far been 
regarded as entirely an empirical formula which 
expresses a fact, without anyone being able to 
state why the relation expressed by the formula 
should exist” (p. 102). The recent work of Bohr 
and others in this field might at least have been 
NO. 2457, VOL. 98] 
[ NOVEMBER 30, 1916- 
mentioned. Even facts are sometimes misstated, 
as will be seen from the two following passages : 
“The amplitude of some rays, such as X-rays, 
goes down to the infinitesimal” (p. 84); and 
“. .. gravitation itself has its limitations, in 
respect of the distance through which it can effec- 
tively operate, and its power is also affected by 
the internal heat or temperature of the body” 
(p- 125). Many of the fundamental conceptions 
in the theory are at fault, and these insecure 
foundations cannot support the elaborate super- 
structure built upon them. 
FLOTATION OF ORES. 
(1) Concentrating Ores by Flotation. By T. J. 
Hoover. Pp. vit+320. Third edition. (London: 
The Mining Magazine, 1916.) Price 12s. 6d. 
net. 
(2) The Flotation Process. Compiled and edited 
by T. A. Rickard. Pp. 364. (San Francisco: 
Mining and Scientific Press, 1916.) Price 
8s. 6d. net. 
Chews subject treated in these two books is one 
of great and rapidly increasing importance. 
The practical application of flotation methods 
is only about thirteen years old, and already 
the quantity of ore treated by them must 
amount to little, if any, less than 30,000,000 
tons. When it is borne in mind that a large 
proportion of this quantity consists of slimes and 
complex ores that had defied all known methods 
of treatment until flotation processes were intro- 
duced, the economic importance of the subject can | 
be readily appreciated. Furthermore, as Mr. 
Hoover points out in his book, this method is still 
in some respects in its experimental stage, and its 
limits of applicability are being rapidly widened, 
so that there are very good grounds for the opinion 
expressed by him :—‘It would seem at the present 
time a justifiable prophecy that flotation methods. 
of concentration will in the not distant future very 
largely displace gravity methods.” 
(1) The mere fact that the third edition of: 
Mr. Hoover’s work has been called for within 
four years of the appearance of the first edition 
is sufficient testimony to the value attached to it 
by the mining profession. It has from the first 
been accepted, and still remains to-day the 
standard work on the concentration of minerals 
by flotation methods. 
As regards this third edition now before us, this 
has simply been produced by reprinting the 
second edition just as it was, without even at- 
tempting to correct any mistakes, but merely 
with the addition of a new chapter, so as to bring 
it up to date. It is difficult to justify such a 
method, seeing that some of the mistakes that 
have been allowed to stand are really serious. 
Thus it comes as a severe shock to find that Mr. 
Hoover should not only have written, but have 
allowed to remain, such a wholly indefensible 
chemical equation as “KCy+Au=KAuCy”; 
or to find him stating that “the horizontal sur- 
face of a liquid at rest’’ may be considered “the 
limiting surface of a bubble of infinite radius,” 
