~OcToBER 2, 1913] 
manner: a man who instals electricity in your 
dining-room, gas in your kitchen, acetylene in 
your billiard room, and candles in your bedroom. 
But the illuminating engineer of practice is 
generally either a gas or electrical engineer with 
his own particular axe to grind. So much is this 
the case that he may show a marked preference 
(against all sound illuminating engineering doc- 
trine) for a particular species of illuminant in the 
genus which he represents—as, for example, for 
flame arc lamps against all other electrical 
illuminants. 
We do not know whether Prof. H. Bohle calls 
himself an illuminating engineer, but at least he 
has written a book (1) which claims in its sub- 
title to be a treatise on illuminating engineering, 
almost as if this were a mere appanage of elec- 
trical photometry and illumination; and, as one 
of the latest works on the new science, we turn 
to it naturally in the hope that it will more than 
justify that science’s existence. It is disappoiut- 
ing to find little, if anything, more than used in 
our student days to be regarded as legitimately 
within the sphere of electrical engineering. It is 
disappointing, too, to find much inadequate treat- 
ment and, we are afraid, insufficient knowledge. 
Take, for example, the discussion of radiation 
laws in chapter ii. This is far from clear, and 
the statement on p. 21: ‘Coloured bodies 
absorb different parts of the impinged radiation : 
consequently they will radiate different fractions 
of black body radiations, according to the fre- 
quency, i.e. according to the temperature,” is, if 
we understand the author’s meaning rightly, not 
correct. 
The description of the manufacture of carbon 
filament lamps in the same chapter must have been 
obtained from some out-of-date account. The 
criticism of the flame arc lamp on p. 97 is 
equally behind the times. It is stated that ‘“‘on 
long winter evenings the lamps do not hold out 
until the next morning, but must be recarboned 
during the night.” This is untrue of any flame 
lamps except those specially designed for short- 
hour lighting, and there are many flame lamps 
now on the market, and have been for years, which 
burn without recarboning for 7o-100 hours, so 
that it will be seen that the criticisms of the author, 
who writes from Cape Town, would only be justified 
at the poles. Flame lamps burning vertical car- 
bons are actually commended for steadiness as 
against lamps with inclined carbons, the exact 
reverse being the case. We were not surprised 
after this to find on p. 171 that the yellow flame 
are is described as “suitable for decorative illu- 
mination,” as apparently its only sphere of use- 
fulness. 
NO. 2292, VOL. 92] 
NATURE 
127 
We need not, however, labour criticism of details 
such as these: it is only to be regretted that in 
discussing such a progressive subject as the 
manufacture and behaviour of electric lamps the 
author did not take more pains to bring his in- 
formation up to date. 
It is of interest to turn to what may be regarded 
as the more distinctly “illuminating engineering ” 
sections of the book. We are told in the preface 
that this is a combined science of physics and 
physiology, and emphasis is laid on the neglect 
of the physiological side, which led us to expect 
that this would be remedied by the author. The 
physiological discussion in the book is, however, no 
more than is usually to be found in similar works. 
In truth, this plea for physiological investigation 
is, in our opinion, frequently exaggerated. The 
knowledge of a few elementary facts is necessary, 
but beyond this physiological knowledge is not 
needed, and it would be equally true to say that 
it was required as part of the equipment of a good 
tailor. 
The last two chapters, “The Design of Reflectors 
and Shades” and “Illuminating Engineering,” 
show how little the new science really has accom- 
plished. With a few exceptions, which existed 
before the illuminating engineer had arrived, elec- 
tric- lamp shades are still, scientifically, as 
chaotic as ever. The design of shades is, in 
fact, for the most part, an art and should 
continue to be so: if the illuminating engineer 
ever succeeds in making it purely a science, he 
will remove what is one of the recommendations 
of electric lighting—that it lends itself to beauty 
as well as to utility. The chapter on illuminating 
engineering gives a number of directions for 
different classes of lighting which the unbiassed 
would admit are no more than a restatement of 
the common-sense practice of years—almost cen- 
turies. 
We cannot omit reference to a novel procedure 
in the numbering of figures and equations. Thus 
the fifth figure in the fourth chapter is numbered 
Fig. 4.05: this is intended to facilitate reference. 
It has quite the contrary effect and we trust will 
not be imitated. 
(2) Dr. Allmand’s treatise is one of the most 
comprehensive and at the same time one of the 
best treatises on applied electrochemistry that we 
can call to mind in the English language. The 
first part, covering fourteen chapters and 194 
pages, deals with the theoretical side of the sub- 
ject. To write a complete exposition of the 
theoretical side of electrochemistry, it would 
almost be necessary to write a complete chemical 
treatise coupled with a much shorter discussion 
of the fundamental electrical phenomena. It is 
