
May 4, 1871] 
NATURE 
17 

mined to establish in London, Dr. Hofmann proceeds to a nar- 
~rative of the difficulties experienced by the new school in the 
deficiency of the money received from the fees of students to 
ineet the necessary expenses as well as the debt incurred by the 
outlay for building. At this stage the college narrowly escaped 
the entire abandonment of its primary object, the advancement 
of science by means of practical instruction and original re- 
szarches, to sink into a mere commercial undertaking for con- 
ducting analyses. To the influence of Sir James Clark, one of 
the earliest friends of the College, was mainly due the ultimate 
success of the efforts of the Council to induce the Government to 
adopt the College as the chemical department of the Museum of 
Practical Geology ; since which period its career of usefulness 
has been unchecked.—Dr. A. E. Sansom follows with an article 
on ‘‘The Theory of Atmospheric Germs,” in which he records the 
investigations on this subject which have been conducted to the 
present time, especially those of Hallier and Bastian ; and sums 
up adversely to the theory of abiogenesis.—Mr. Mungo Ponton, 
in his short paper on Molecules, Ultimates, Atoms, and Waves, 
suggests the use of the term ‘‘ molecule” to denote the particles 
of chemical compounds; ‘‘ultimate,” those of chemical ele- 
ments ; and ‘‘atom,” the assumed constituents of those ultimates, 
themselves incapable of further analysis.—Prof. Piazzi Smyth 
occupies no less than thirty-eight pages with the conclusion of 
his article on ‘The Great Pyramid of Egypt from a modern scien- 
tific Point of View.”—Sir William Fairbairn has some very prac- 
tical remarks on Steam Boiler Legislation, in which he details 
the failure of voluntary associations for the purpose of diminishing 
the loss of life and property occasioned by the use of defective 
boilers, and advocates the enforced legal testing of boilers by 
competent authorities, maintaining that itis clearly the duty of 
the Government to interfere on behalf of those whose lives are 
jeopardised, and to enact that no boiler shall be worked unless 
periodically examined and certified.—The last article is an 
account of the Eclipse of Jast December, by Mr. R. A. Proctor. 
Notices of books and a record of the progress of science in the 
departments of light, heat, electricity, meteorology, mineralogy, 
mining, metallurgy, engineering, geology and palzontology, and 
botany, fill up a very good number. 
THE numbers of the American Naturalist for March and 
April contain some good articles. The Polarity of the Compass 
Plant (Silphium laciniatum) is a subject which has recently 
attracted attention, and Mr. W. F. Whitney’s short article under 
this title sams up what is at present known about its causes.— 
Mr. J. A. Allen’s paper ina previous number on ‘*The Flora of 
the Prairies” is followed by one on ‘*The Fauna of the Prairies.” — 
Dr. G. H. Perkins describes some interesting relics of the 
Indians of Vermont, illustrated with woodcuts.—Mr. F. W. 
Vogel has an article on the Principles of Bee Breeding. —Mr. 
E. L. Greene gives an account of the Spring Flowers of Colo- 
rado.—Mr. W. Wood has 2 valuable article on the Game 
Falcons of New England ; and Dr. A. S. Packard, jun., one on 
Bristle-tails and Spring-tails, the Lepismas and Poduras, illus- 
trated by plates, and containing a very full account of this inte- 
resting family. In both numbers are also reviews of recent works 
on natural history, and many interesting paragraphs of intelli- 
gence under the heads of botany, zoology, geology, anthropology, 
and microscopy, original or compiled, from American and 
foreign sources. 


SOCIETIES AND ACADEMIES 
LonDON 
Royal Society, April 27.—‘‘ On the Increase of Electrical 
Resistance in Conductors with rise of Temperature, and its 
application to the Measure of Ordinary and Furnace Tempera- 
tures ; also on a simple Method of measuring Electrical Resist- | 
ances.” By C. W. Siemens, F.R.S., D.C.L. 
The first part of this paper treats of the question of the ratio 
of increase of resistance in metallic conductors with increase of 
temperature. r J 
The investigations of Arndtson, Dr. Werner Siemens, and Dr. 
Matthiessen are limited to the range of temperatures between | 
the freezing and boiling-points of water, and do not comprise 
platinum, which is the most valuable method for constructing 
pyrometric instruments. 
Several series of observations are given on different metals, in- 
cluding platinum, copper, and iron, ranging from the freezing- 
oint to 350° Cent. ; another set of experiments being also given, 

extending the observations to 10002 Cent. These results are 
planned on a diagram, showing a ratio of increase which does not 
agree either with the former assumption of a uniform progression, 
or with Dr. Matthiessen’s formula, except between the narrow 
limits of his actual observations, but which conforms itself to a 
parabolic ratio, modified by two other coefficients, representing 
linear expansion and an ultimate minimum resistance. 
In assuming a dynamical law, according to which the electrical 
resistance of a conductor increases according to the velocity with 
which the atoms are moved by heat, a parabolic ratio of increase 
of resistance with increase of temperature follows; and in 
adding to this the coefficients just mentioned, the resistance x for 
any temperature is expressed by the general formula, 
r=al?+BT+y, 
which is found to agree very closely both with the experimental 
data at low temperatures supplied by Dr. Matthiessen, and with 
the author’s experimental results, ranging up to 1000° Cent. He 
admits, however, that further researches will be necessary to 
prove the applicability of the law of increase expressed by this 
formula to conductors generally. 
In the second part of this paper it is shown that, in taking 
advantage of the circumstance that the electrical resistance of a 
metallic conductor increases with an increase of temperature, an 
instrument may be devised for measuring with great accuracy the 
temperature at distant or inaccessible places, including the interior 
of furnaces, where metallurgical or other smelting operations are 
carried on. 
In measuring temperatures not exceeding 100° Cent., the 
instrument is so arranged that two similar coils are connected by 
a light cable containing three insulated wires. One of these coils, 
‘the thermometer-coil,” being carefully protected against 
moisture, may be lowered into the sea, or buried in the ground, 
or fixed at any elevated or inaccessible place whose temperature 
has to be recorded from time totime ; while the other, or ‘‘ com- 
parison-coil,” is plunged into a test-bath, whose temperature is 
raised or lowered by the addition of hot or cold water, or of 
refrigerated solutions, until an electrical balance is established 
between the resistances of the two coils, as indicated by a galva- 
noscope, or by a differential voltameter, described in the second 
paper, which balance implies an identity of temperature at the 
two coils. The temperature of the test-solution is thereupon 
measured by means of a delicate mercury thermometer, which at 
the same time tells the temperature at the distant place. 
By another arrangement the comparison-coil is dispensed with, 
and the resistance of the thermometer-coil, which is a known 
quantity at zero temperature, is measured by a differential volta- 
meter, which forms the subject of the second paper; and the 
temperature corresponding to the indications of the instrument is 
found in a table, prepared for this purpose, in order to save all 
calculation. 
In measuring furnace temperatures the platinum-wire consti- 
tuting the pyrometer is wound upon a small cylinder of porce- 
lain contained in a closed tube of iron or platinum, which is 
exposed to the heat to be measured. If the heat does not exceed 
a full red heat, or, say, 1000° Cent., the protected wire may be 
left permanently in the stove or furnace, whose temperature has 
to be recorded from time to time ; but in measuring temperatures 
exceeding 1000” Cent., the tube is only exposed during a measured 
interval of, say, three minutes, to the heat, which time suffices 
for the thin protecting casing and the wire immediately exposed 
to its heated sides, to acquire within a determinable limit the 
temperature to be measured, but is not sufficient to soften the 
porcelain cylinder upon which the wire is wound. In this way 
temperatures exceeding the welding-point of iron, and approach- 
ing the melting-point of platinum, can be measured by the same 
instrument by which slight variations at ordinary temperatures 
are told. A thermometric scale is thus obtained embracing 
without a break the entire range. 
The leading wires between the thermometric coil and the mea- 
suring instrument, which may be under certain circumstances 
several miles in length, would exercise a considerable disturbing 
influence if this were not eliminated by means of the third lead- 
ing wire before mentioned, which is common to both branches 
of the meas«ring instrument. 
Another source of error in the electrical pyrometer would arise 
through the porcelain cylinder npon which the wire is wound be- 
coming conductive at very elevated ten:peratures ; but itis shown 
that the error arising through this source is not of serious import. 
The third part of the paper is descriptive of an instrument for 
measuring electrical resistance without the aid of a magnetic 
