160 
SPANG’S LIGHTNING PROTECTION. 
A practical treatise on liyhtning-protection. By 
Henry W. Spanc. New York, Van Nostrand, 
1883. 63 p. 8°. 
Tuts is a new and enlarged edition of the 
author’s treatise on lightning-protection, pub- 
lished in 1877. ‘The book contains altogether 
too many good things to be bad, and too many 
bad things to be entirely good. There is 
a wholesale condemnation of all systems and 
methods other than those described, which is 
a little perplexing, until one discovers, and in 
fact the author confesses, that it is issued with 
a view of effecting a general introduction of a 
patented system of lightning-conductors. The 
business air which pervades the whole is thus 
clearly explained. 
The author frequently pronounces against 
the ‘ lightning-rod men and scientists,’ attribut- 
ing the blunders of the former to the mistakes 
of the latter. A brief examination of his book 
will suffice to fully acquit him of the charge 
of belonging to the latter class ; and it must be 
confessed, that the many excellent rules which 
he has emphasized oblige us to rank him con- 
siderably above the general average of the 
former. The general principles of lightning- 
protection, as presented, are in the main cor- 
rect; and, as general principles, they deserve 
a wide dissemination. The particular system 
urged as the only efficient one is more compli- 
cated, and, even if it were not patented, more 
expensive than is necessary. Some novel 
statements are made, concerning what light- 
ning ‘ will do ’ under certain circumstances, in 
the same paragraph in which the author be- 
moans the ignorance shown by scientific men 
on the subject of lightning-protection. 
The author does not seem to be aware of the 
existence of what is doubtless the most com- 
plete and authoritative treatise on the subject 
yet published, — the elaborate ‘ Report of the 
lightning-rod conference,’ edited by G. J. Sy- 
mons, f.R.S. This conference was made up 
of delegates from the London meteorological 
society, the Royal institute of British archi- 
tects, the London society of telegraph engi- 
neers and electricians, the London physical 
society, and two co-opted members, Profs. W. 
K. Ayrton and D. E. Hughes. 
The examination of the various problems 
presented was exhaustive, and the code of rules 
for the erection of lightning-conductors pub- 
lished in the report is simple and easily under- 
stood. ‘The proper construction of an efficient 
lightning-conductor is, after all, a matter of no 
great difficulty, and of comparatively little ex- 
pense. The inauguration of a proper system 
SCIENCE. 
[Vou. ILI., No. 5B. 
of testing conductors would certainly reveal 
some astonishing facts in regard to the efficien- 
cy of rods as generally erected, elaborate and 
expensive as they often are. ‘The wide circu- 
lation of the rules adopted by this conference — 
would undoubtedly be the means of bringing — 
about a much-needed reform in this direction. 
COHN’S ‘DIE PFLANZE 
Die pflanze: Vortrdge aus dem gebiete der botanik. 
Von Dr. FERDINAND Coun, professor an der 
Universitat zu Breslau. Breslau, Kern, 1882. 
8+ 512 p. 4°. : 
Tus elaborately gotten up book of over five 
hundred pages comes to us as a contribution to 
general literature, and does not address itself — 
to the scientific botanist, except as he is inter- 
ested in a popular presentation of botanical 
facts and problems with which he is supposed 
to be more or less familiar. Dr. Cohn believes 
it to be the duty of those versed in any branch 
of science to produce a literature which shall 
invite a large circle of readers to an interested 
acquaintance with their chosen science. ‘‘ Nor 
are they to recoil from this task,’’ says he, 
‘* because of the difficulties which present them- 
selves for satisfactory solution, or because 
popular writings on natural science have been 
undervalued by many.’’ Actuated by his con- 
viction, Dr. Cohn has collected the addresses 
which he delivered at various places in Ger- 
many between the years 1852 and 1881, and, 
while retaining their original form, has remod- 
elled them sufficiently to bring them up to date 
and compact them into a shapely whole. 
In the preface the author sets forth a difficulty 
which besets the popular lecturer on scientifie 
topics, —one which doubtless every one who 
has tried this style of address has fully real- 
ized,—namely, the meagre knowledge and hazy 
comprehension with which the majority of hear- 
ers listen to his words, necessitating so long a 
dwelling on the elementary facts of the topic 
that little time is left for the consideration of 
the more recondite and interesting points. 
If we may be allowed to judge, Dr. Cohn 
has overcome this difficulty to a large degree 
in a very happy manner. He devotes the first 
lecture, entitled ‘ Botanical problems,’ to a 
brief history of the development of botany, and ~ 
an explanation of some of the elementary prin- 
ciples of the science, thus paving the way for 
subsequent discussion of more special matters. 
Some idea of the variety of the topics treated 
may be gained from the titles of the sixteen” 
lectures, which are as follows: ‘ Botanical prob- 
lems,’ ‘ Goethe as a botanist,’ ‘ The cell state,” 
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