368 
NATURE 
[JANUARY II, 1917 
with corresponding singularities. A mathematical 
student will find it an excellent exercise to dualise 
all the theorems contained in this volume. Again, 
in discussing cyclides, the author has missed the 
chance of referring to Lie’s one-one corre- 
spondence of lines and spheres in space. A real 
cyclide is the envelope of a real sequence of 
spheres; Lie’s transformation leads to a sequence 
of complex lines, and it would be interesting to 
see what the cyclide corresponds to. 
Prof. Jessop duly appreciates the late 
R. W. H. T. Hudson’s book on Kummer’s sur- 
face; he has himself composed a work of the 
same kind, in the sense that it is a valuable intro- 
duction to some of the latest results obtained by 
geometricians. GBM: 
OUR BOOKSHELF. 
A Manual of Fire Prevention and Fire Protection 
for Hospitals. By Dr. O. R. Eichel. Pp. v+ 
69. (New York: John Wiley and Sons, Inc. ; 
London: Chapman and Hall, Ltd., 1916.) 
Price 4s. 6d. net. 
Tue British Fire Prevention Committee, whose 
fire surveyors have been undertaking the fire pre- 
cautionary arrangements in innumerable hospitals 
throughout the country, recently indicated in one 
of its reports that medical men who are prone to 
forethought are particularly ready to take precau- 
tions in such establishments as hospitals. We 
therefore specially welcome the little book before 
us, from the pen of a medical man connected with 
the New York State Department of Health. As 
it is largely based on American practice, much 
of the detail does not hold good in this country, 
yet the principles enunciated are sound. 
Taking up a question of detail and having 
regard to the unfortunate tendency of some hos- 
pitals in this country to purchase .dry-powder 
extinguishers, we observe that the author deals 
with them as follows :— 
Dry-Powber ExtincuisHers.— These are the 
least reliable and most inefficient extinguishers 
known. Unfortunately, they are also very widely 
used, and can be found in many hospitals. . . .” 
Again, referring to another unfortunate type of 
fire appliance (sic), the glass hand grenade, which 
will be found in many hospitals, the author says :— 
GRENADE Typr.—‘ These types usually consist of 
bottles containing fluids, a large percentage of 
which is water, and are of so little value as to be 
practically worthless. The false sense of security 
which may result from their presence, and the time 
lost in attempting to quench the fire with them, 
may be very dangerous. They are hardly equiva- 
lent in value to a pitcher full of water. . . .” 
Whilst we have mentioned specific examples 
of the author’s comments on appliances, we should 
like to emphasise that he wisely gives fire preven- 
tion precedence to fire extinction. He deals with 
lighting hazards, heating hazards, etc. He also 
has some words to say on the organisation of the 
staff from the fire point of view, i.e. what he 
describes as the “Hospital Fire Department.” 
NO. 2463, VoL. 98] 
| The Portland Cement Industry. By W. A. 
Brown. Pp. x+158. (London: Crosby 
Lockwood and Son, 1916.) Price 7s. 6d. net. 
THE cement industry presents striking  re- 
semblances to the aniline dyes industry. 
first aniline dye was discovered and manufactured 
in England. Afterwards the sustained attention 
devoted to the subject by trained minds in Ger- 
many so changed the conditions through the 
of production that eventually a monopoly was 
acquired. Similarly, Great Britain first produced 
cement—Parker’s (afterwards called Roman) 
cement in 1796 and Portland cement in 1824, 
to which may be added reinforced concrete 
(covered by Elkinson’s patent) in 1854. So, too, 
though partly from different causes, the cement 
industry has developed far more rapidly in Ger- 
many and the United States than here. The 
remarkable progress in America is attributed to 
the close co-operation during the past fourteen 
years of Associations of Cement Manufacturers 
and Cement Users. Fortunately, British cement 
machinery is now equal to any made in Germany, 
though it cannot compare favourably with 
American machinery. The improvement of 
cement has been facilitated by the general adop- 
tion of the “British Standard Specification,” but 
ample scope remains for research with a view to 
increased economy and efficiency in the manu- 
facturing processes. 
now managing a large modern cement works in 
South Wales. Special attention is bestowed on 
the vital question of costs, particularly working 
may be profitably consulted by those interested 
in the industry. There are numerous illustrations, 
including thirty-six full-page plates, .and some 
notes on physical testing ccnstitute a valuable 
feature. J. Ae 
Actualités Scientifiques. Le Principe de Rela- 
tivité. By E.-M. Lémeray. Pp. 155. (Paris: 
Gauthier-Villars et Cie, 1916.) Price 3 fr. 75 c. 
THE aim of this work is not to give a historical 
or critical survey of the development and signifi- 
cance of the principle of relativity, but rather to 
theory so far as they are independent of all hypo- 
theses as to the electrical constitution of matter. 
the fundamental law of inertia, the last only for the 
most restricted case. From these the author de- 
velops conclusions as to the limitations to be 
placed upon the theorem of equality of action and 
reaction, upon the law of gravitation, and upor 
the meaning of mass. The extent to which tne 
principle agrees with and requires experimental 
results is barely touched upon, but this is prob- 
ably because the book is the record of a séries 
cular point of view. 
The’ 
introduction of new colours and cheaper methods - 
The book before us is eminently practical, and 
deserves serious consideration because the author. 
has had important American experience, and is 
costs for economical production, and the book 
develop some of its consequences for dynamical 
Three principles are assumed : the constancy of the. 
velocity of light, the principle of virtual work, and, 
of lectures aiming at a presentation of a parti- 
