MARORE 


THURSDAY, MAY 6, 10915. 


THE TECHNOLOGY OF ILLUMINATION. 
Modern Illuminants and Illuminating Engineer- 
ing. By Leon Gaster and J. S. Dow. Pp. xiv+ 
462. (London: Whittaker and Co., 1915.) 
Price 12s. 6d. net. 
HEN a new branch of science, art, or in- 
dustry becomes recognised, the literature 
on the subject might at first be expected to be 
scant in quantity and meagre in scope. But illu- 
minating engineering is a new branch only in so 
far that attempts have been made to collect and 
arrange scattered facts and principles, and very 
few individuals call themselves illuminating en- 
gineers. So far as means, methods, and appli- 
ances for producing artificial light are concerned, 
the new movement has done little else than to 
record ancient and modern practice, but certain 
advances have been made on the scientific side 
by the development of photometry, and the exten- 
sion of theoretical considerations of the distri- 
bution of illumination which are not to be found 
in text-books on optics. Some attention has been 
given to the subject of “glare” which is difficult 
to define, and to the artificial production of light 
not differing visually from ordinary daylight. 
Having regard to the keen rivalry between the 
advocates of gas and of electric lighting, the 
success of an illuminating engineering society at 
one time appeared to be doubtful. It was founded 
in 1909, and has as its official journal the JIlu- 
minating Engineer. The membership has reached 
nearly five hundred, and many useful papers and 
discussions have resulted. This has been largely 
due to the tact and zeal of Mr. L. Gaster and Mr. 
J. S. Dow, the editors of the journal and the 
secretaries of the society. Even if the former of 
these were not a linguist or had a taste for 
antiquarian research and a genius for bringing 
competitors into harmony, and if the latter were 
not trained in physics and had not done any ori- 
ginal work in photometry, they would have been 
in possession of a vast amount of material for a 
book, and well qualified to use it. 
In accordance with the traditional opening of a 
Friday evening discourse at the Royal Institution, 


the first chapter begins with “the very earliest , 
conceptions of light”? in remote antiquity, and its 
use “among primitive peoples,” and runs through 
history up to the Home Office Departmental Com- 
mittee on Illumination, and the formation of the 
International Photometric Commission. The 
second chapter deals with gas burners, and does 
not touch on the chemistry or the making of gas. 
The section on high-pressure gas is compressed 
into only about five pages. The third gives as 
NO 2375, VOL. 95] 
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MAY 29 1915 

253 
much on electrie Yagiati ae: wauseUn be packed into 
thirty-six pages, while the fourth describes oil, 
petrol-air gas, and acetylene lighting. These 
constitute one-third of the book, and appear at 
first to be of a sketchy character, but almost every 
page has foot-notes, and most of these refer 
to English and foreign periodical literature. A 
bibliography is provided at the end, but it does 
not include more than a small portion of the 
publications referred to in the valuable foot-notes. 
The fifth and sixth chapters on the human eye 
and colour vision are a useful epitome. The last 
half of the book consists of chapters the 
measurement of light and illumination, shades and 
reflectors, problems of interior and of outdoor 
lighting. These are well illustrated by reproduc- 
tions of photographs, many of which have ap- 
peared in the Illuminating Engineer. Although 
this does not profess to be a treatise or even a 
text-book, an omission or two must be noticed. 
Polar curves are given in considerable numbers, 
and the solitary place in which an integral expres- 
sion is used warns the reader against a common 
mistake which is sometimes made in deducing 
mean spherical candle-power from such a curve. 
“The well-known Rousseau method,” which 
achieves this result graphically, is not described 
or even foot-noted, but is merely alluded to. The 
Ulbricht globe which is experimentally used for 
the same purpose has a full-page illustration and 
a foot-note with eight references, but only eleven 
lines are allowed for a description of it. Prof. 
Clinton has shown that the illumination of a room 
may be pre-determined by calculation, and pos- 
sibly his treatment was not suitable for a book 
of this type, but, on the other hand, there are 
several rule-of-thumb methods and tables for find- 
ing how many lamps or how much candle-power 
or flux in lumens are required for interior work, 
and some of these might have been included. An 
American trading concern cannot perhaps be 
blamed for giving the name ‘‘X ray” to a type of 
reflector, but it should not be mentioned without 
a disparaging “so-called.” 
The subject is still developing so rapidly that it 
must have required some courage to produce a 
volume of this kind, and it is so wide that to 
decide the proportion to be allowed to different 
sections must have been a matter of difficulty. 
Such questions of proportion are necessarily 
matters of opinion, and books, after all, are what 
publishers allow authors to offer us, and not what 
the reviewers think or even what the readers 
may desire that they should be. Some would like 
more mathematics, others data on economical 
points. The authors have succeeded admirably in 
the task which they have set themselves, and the 
book is well produced. 
on 
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