340 
NATURE 
[NovEMBER 20, 1913 
ployed to transmit the intelligence of an event to 
a distant place. 
It may be true that it is impossible to conceive 
of a body moving relatively to an observer with 
velocity greater than that of light. But we can, 
and do, work with f-particles of radium, and we 
can imagine two of these expelled in opposite 
directions from a source of radium at rest rela- 
tively to the earth, and therefore, in ordinary 
parlance, having a velocity relatively to one 
another nearly twice that of light. This, of 
course, in no way questions or minimises the im- 
portance of the principle of the great German 
mathematical physicist in its own field, but science 
is evér sceptical of restrictions which it is told 
must necessarily and for all time limit its power 
of disentangling the phenomenon from the appear- 
ance of the phenomenon. In any case the author 
deserves success in thus including in this conscien- 
tious review of modern electrical theory some of 
the modern conceptions which are at once the most 
foreign to our habits of thought and the most diffi- 
cult to appreciate at their true worth. Successful 
the volume undoubtedly is in its purpose of pro- 
viding serious students acquainted with the older 
physics an introduction to the newer theories. 
(2) This collection of ten lectures by as many 
authorities treats in simple and clear fashion with 
some of the special departments of physical science 
nov: most to the fore. Brownian movement, the 
subject of high vacua or ultra-rarefied gases, and 
the relations between matter and the ether are the 
only three topics which can claim even thirty 
years of history. Three more deal with the elec- 
tron in one or other aspect—electro-magnetic 
dynamics, the electronic theory of metals, and 
ionisation by collision and the electric spark— 
and two with radioactivity, the radiations of the 
radioactive substances, and their successive trans- 
formations. Lastly, two of the newest concep- 
tions, the quantum theory of energy and the 
magneton theory, complete the volume, which 
will prove as useful and interesting as earlier 
publications on similar lines by the Société fran- 
gaise de Physique. 
(3) The third volume is a collection of some of 
the most interesting and beautiful discoveries of 
Prof. R. W. Wood, issued by the Columbia Uni- 
versity under the E. K. Adams fund for physical 
research. They include the notable contributions 
to resonance spectra and radiations, first with 
iodine, then from mercury vapour, which have 
enabled the vapour arising from a cold surface of 
mercury.to be photographed, and going on to 
experiments with heat waves of more than o'r mm. 
wave-length, analogous to those with Herzian 
waves, in which a “dew” of condensed mercury 
NO. 2299, VOL. 92| 
globules deposited on quartz was employed for ; 
the resonator. This in turn leads to some extra- “3 
ordinary, still incomplete, observations on the elec- 
tric conductivity of ruled silvered glass gratings, — 
in spite of the complete severance of the silver 
film by the diamond. ° 
Lastly must be mentioned some attempts to 
photograph the lunar surface through screens 
transmitting only yellow, violet, and ultra-violet 
light respectively. These photographs reveal the 
presence of a remarkable deposit round the crater 
of Aristarchus, which very probably may be 
sulphur, and foreshadow a method for carrying 
out a limited petrological survey of the lunar 
surface. It is a pity that the volume does not 
appear to be for sale, for many no doubt would 
be glad to secure this well-illustrated collection of — 
modern experimental researches by one of its — 
greatest masters. FREDERICK SODDY. 
THE THRESHOLD OF SCIENCE—AND 
BEYOND. 
(1) Zoology. By Prof. E. Brucker. Pp. xili+ 219. 
(London : Constable and Co., Ltd., 1913.) Price 
2s. net. 
(2) Some Secrets of Nature. Short Studies in Field 
and Wood. With an introduction by W. J. r 
Burton. Pp. xiv + 144 + plates. (London : 
Methuen and Co., Ltd., n.d.) Price 1s. éd. 
(3) Lhe Romance of Nature. Studies of the Earth — 
and its Life. With a preface by the Rev. A. 
Thornley. Pp. xix+164+x plates. (London: — 
Methuen and Co., Ltd., n.d.) Price 2s. 
(4} In the Lap of the Lammermoors. By W. 
McConachie. Pp. xii+315- (Edinburgh and 
London: William Blackwood and Sons, 1913-) 
Price 5s. net. 
(1) ). of the many ways of beginning the 
study of zoology is to take a survey of © 
the whole animal kingdom, working from the 
simple to the complex, never going very deeply 
into anything, but using now this, now that, to 
illustrate a principle. That is what Prof. Brucker — 
has done, and it is a feat to have done it so 
clearly and in such simple language. If the reader, © 
young or old, is able to touch and handle, as well 
as read about, even a tenth of the creatures dis- 
cussed, he will have got far across the threshold — 
of the science—to use the phrase which gives its — 
name to this new series. To our thinking there is 
far too much in the book for an introduction, but 
that is largely a matter of opinion, and it is doubt- 
less what students say of most courses of elemen- : 
tary instruction which their professors after much — 
thought on the subject decide to deliver. Be this — 
as it may, the author of this little book is evi- 
