542 
NATURE 
[ Oct. 7, 1886 — 
other pests. One of the great difficulties in growing 
orchids and other plants under artificial conditions is 
due to the injury caused by insects. 
knowledge of chemistry and of vegetable physiology 
would find, we believe, a profitable field of inquiry in this 
direction. Amateurs and the trade alike have dealt with 
this difficulty by rule of thumb for generations, and con- 
fined themselves to smoking plants with tobacco in various 
shapes, and treating them with quack insecticides. So 
far as tobacco-smoke is effectual, its effect is probably 
due to the nicotine it contains. There can be no insuper- 
able difficulty in charging the air of a closed house with 
nicotine fumes sufficiently to destroy insects, and in 
thereby getting rid of the pungent and injurious smoke 
produced by burning coarse tobacco and brown paper. 
In conclusion we may express a hope that this work will 
not come to a premature end, like some of its prede- 
cessors, but live to fulfil the promise of the parts here 
noticed. 
ARC AND GLOW LAMPS 
Arc and Glow Lamps. A Practical Hand-Book on 
Electric Lighting. By Julius Maier, Ph.D. (London: 
Whittaker and Co., and G,. Bell and Sons, 1886.) 
WE should have been glad if it had been possible to 
speak more favourably of Dr. Maier’s work than 
can be done after a conscientious reading of it; for Dr. 
Maier has made himself so thoroughly master of our 
language, and has taken such obvious pains to acquaint 
himself with the literature of electric lighting, that we | 
cannot help wondering how so able a man has produced 
such a disappointing treatise. Much of the work appears 
to have been translated from Merling’s and other German 
books on electric lighting. Perhaps it is to this com- 
posite origin that the defects are due which a reviewer is 
bound to point out. 
The first 82 pages are occupied by generalities such as 
the laws of production of heat in the circuit, the efficiency 
of dynamos, electric and photometric measurements. 
Then come 60 pages upon arrangements of leading wires 
and of lamps in installations for electric light, including 
the so-called “secondary generators” or induction coils 
for distributing alternating currents. At p. 140 we at last 
reach arc lamps, the principal types of which are described 
with care. Twelve pages are allotted to the now almost 
obsolete electric “ candle,” and at p. 263 we enter upon 
the glow lamps. These are described all too briefly, 
especially so far as relates to the details of manufacture ; 
but the data as to tests of efficiency and durability of the 
lamps are most satisfactorily summarised. This chapter 
includes an abstract of the tests made by the Philadelphia 
Committee, whose method of testing the lamps and of 
deducing the “ mean spherical intensity” of the illumina- 
tion is perhaps more scientific than that of any of the 
numerous Exhibition committees who have reported on 
electric lamps. The book concludes with special chap_ 
ters on the application of electric light to lighthouses, 
ships, mines, railway trains, photography, and operative 
surgery. y 
There are several contradictory statements in Dr. 
Maier’s book. On p. 27c he tells us that after the inven- 
tions of Greener and Staite in 1846 electric lighting fell 
Any one with a | 
completely into oblivion till 1873, when Lodyguine took 
up the question. Yet on p. 148 we find a description 
of improvements made in 1857 by Lacassagne and Thiers, 
and on p. 362 we find that electric light has been used 
for stage purposes ever since the production of Meyer- — 
beer’s opera of “ Le Prophéte” in 1846. The records of — 
the English Patent Office between 1846 and 1873 show — 
abundant evidence to negative Dr. Maier’s statement. 
In that interval came the invention of the lamps of Serrin, _ 
Chapman, Way, and Browning, and the successive im- 
provements of Holmes, Siemens, the Varleys, Wheatstone, ‘ 
Wilde, and Gramme in the magneto- and dynamo-electric 
generators for lighting purposes. On p. 32 it is stated 
that the drawback of the system of arranging lamps in 
series in one circuit lies in the fact that the individual 
lamps are not independent of one another; yet on p. 94 
and p. 184 it appears that there are means by which any 
lamp is made quite independent of all the other lamps in ; 
the series. z 
We object entirely to Dr. Maier’s classification of arc _ 
lamps into “monophotal” and “polyphotal”; these high- 
sounding names being respectively applied by him to 
lamps that will not work, and those that will work, when 
more than one is placed ia series in the same circuit. 
The distinction is entirely misleading: for the question 
whether one or many lamps can be worked together 
depends quite as much on the dynamo as on the lamps. 
Every one knows that modern dynamos are so designed 
as to work under one of two standard conditions: they 
must either yield a constant current in the line, or else 
must maintain a constant difference of potential between 
the distributing mains. Asa rule arc lamps arranged to 
work in series in a constant-current circuit will not work 
if set in parallel across the mains of a constant-potential 
network, and vice versd. The true classification of lamps 
should therefore be into constant-current lamps which 
will work many in series, and constant-potential lamps— 
which will work many in parallel. Probably the only 
lamp that will not fallin one of these two categories is 
the old regulator of Duboscq and Foucault. Most of the 
lamps classified by Dr. Maier_as monophotal, and which 
according to him can only be worked each with its own 
separate dynamo, will work perfectly well in parallel with 
one another on a constant-potential system of mains. 
One consequence of Dr. Maier’s curious classification is 
that when he comes to the Giilcher lamp, which is an 
excellent lamp for lighting in parallel, he cannot put it 
under either head, and it is relegated to miscellaneous” 
lamps. Of the lamps which he describes as polyphotal, 
the very first is Lontin’s modification of the Serrin lamp ; 
but curiously enough the lamp figured and described in 
the text is zo¢ Lontin’s but is the old unmodified Serrin, 
which, though stated by Dr. Maier to be monophotal, is 
really exactly in the same category as Gulcher’s lamp. 
The lamp of Street and Maquaire is stated to be different 
from all other arc lamps in employing a vibratory prin- 
ciple: the author appears not to know that the lamps of 
Clark-Bowman, Newton, and Pieper also have vibrating 
mechanism. Amongst other erroneous points it is stated 
on p. 321 that Edison was the first to point out the 
advantage of high electromotive force in the glow lamp ; 
on p. 324 that the Lane-Fox pump gives “ infinitely better 
results” than the Sprengel or Geissler pumps; on p. 305 
