- 
260 
amounts to saying that a high electromotive force is 
necessary for this end. 
Many experiments continue to be made upon the 
magnetizing-function of steel and nickel. Hugo 
Meyer has experimented with weak magnetizing- 
forces, and finds that, 1°, the magnetizing-function 
has a positive value for a diminishing magnetizing- 
force; 2°, it increases at first with the magnetizing- 
force; 3°, it increases, for weak magnetizing-forces, 
with the temperature. Professor Ewing of Tokio, 
Japan, maintains that soft iron can be far more re- 
tentive of magnetism than steel. His results and 
detailed experiments are awaited with great interest. 
Experiments made in the physical laboratory of 
Harvard university during the year have shown that 
the action of magnetism upon the conduction of heat, 
which has been maintained by several investigators, 
does not exist in magnetic fields which are at least 
ten thousand times the strength of the earth’s field 
in Cambridge; and doubts are thrown upon such an 
action in general. 
Hall’s phenomenon continues to attract attention. 
As is well known, Mr. Hall has shown that an elec- 
trical current, traversing a thin plate of metal which 
is placed in a strong magnetic field perpendicular 
to the lines of magnetic force, has an electromotive 
force exerted upon it. At first it was supposed that 
this showed that an electrical current could be affect- 
ed independently of the medium through which it 
passes. Mr. Hall, however, showed that the effect 
was different in different metals, and that the first 
conclusion was untenable. Aug. Righi has modified 
Mr. Hall’s apparatus, and has discovered that the 
action in bismuth is extraordinary, being five thou- 
sand times as strong as in gold. The effect in bis- 
muth can be obtained with a permanent magnet; and 
Righi hopes to show the phenomenon by means of so 
feeble a force as the earth’s magnetism. 
Edlund has broached a theory that a vacuum con- 
ducts electricity, and that the high resistance in rari- 
fied tubes is due to a contrary electromotive force at 
the electrodes in the Geissler tubes. He showed, 
that, without the employment of electrodes, one can 
excite an induction current in a Geissler tube which 
is sufficient to produce light. He maintains that this 
would be impossible if the highly rarified gas were 
an insulator. 
Among the comparatively new electrical instru- 
ments which have been described during the year, 
are modifications of Lippman’s electrometer. This 
consists, as is well known, of a capillary tube, con- 
necting at one end with a comparatively large recep- 
tacle of mercury, and at the other with a vessel 
containing diluted nitric acid. The superficial ten- 
sion at the end of the thread of mercury in the cap- 
illary tube is changed by a difference of electrical 
potential. The terminals of a Daniell cell —con- 
nected, one with the acid, and the other with mercury 
— cause a movement in the mercury-column, which 
gives a standard by which electromotive forces in 
general can be estimated. The instrument is very 
sensitive, but requires great care to prevent inaccurate 
measurements. A. Chevet has devised a modifica- 
SCIENCE. 
‘mometer enters the acidulated water. 
tion of Lippman’s instrument, which he claims will 
show a difference of potential of ton to tob00 Of a 
Daniell cell. Two flasks, with lateral orifices on the 
same horizontal line, are connected through these 
orifices by the tube of a thermometer open at both © | 
The bulb-end enters the flask A, which is 
ends. 
filled with mercury. The capillary end enters the 
a 
flask B. This latter flask is filled partly with mercury, 
and partly with water acidulated with a tenth part 
The capillary end of the ther- 
A platinum 
wire, P, insulated by a vitreous covering so as not to 
be in contact with the acidulated water, is in contact 
with the mercury of flask B. Another platinum 
wire, J, is in contact with the mercury of the flask A. 
By means of a commutator a difference of potential 
can be intercalated between the ends of P and N. 
The heights of the mercury and water in the flasks A 
and B are such, that, P and WN being connected by a 
metal wire, the surfaces of separation of the liquids 
are in the region of the capillary portion of the larger 
end of the thermometer-tube. The movements of the 
meniscus is observed with an eye-piece. Electrom- 
eters of the class of Lippman’s can be constructed 
by any one at comparatively no expense, and are 
already used by physiologists. Hard-headed physi- 
of sulphuric acid. 
- 
cists, however, regard such instruments with con- — 
siderable doubt when quantitative measurements are 
to be made. The subject of electrometers in gen- 
eral is very important from the point of view of 
the exigencies of meteorological bureaus and the 
signal-service. Modifications of Sir William Thom- 
son’s instruments still maintain their pre-eminence. 
Among these modifications is an instrument invented 
by Edelmann of Munich, in which the box-shaped 
quadrants of Thomson are replaced by cylinders, and 
the flat needle also by a suspended cylinder-shaped 
needle. The writer of this article remembers to 
have seen, ten years ago, an instrument similar to, 
that of Edelmann, which had been devised by Mr. 
Moses G. Farmer, formerly of the U. S. torpedo sta- 
tion at Newport. It is said that the insulation of 
Edelmann’s instrument is not perfect. - - 
The cause of the electricity of the atmosphere is 
still unknown. The experiments of Freeman and 
Blake have apparently shown that the evaporation 
of pure water does not produce electricity. Kalischer 
has lately tested the question whether the condensa- 
tion of aqueous vapor is a source of electricity. 
used a modification of Thomson’s electrometer, and 
connected it, with suitable precautions, with twelve 
large beakers which were covered with tinfoil and 
were filled with ice. 
protected from extraneous electrical influences. The 
condensation of aqueous vapor upon the beakers pro- 
duced no electrical effect which could be observed. 
The criticism that can be made upon the experiments 
These beakers, in turn, were: 
He 
of Blake and Freeman is, that on the earth’s surface — 
an immense evaporation results from salt water, and 
impurities in the water may produce a state of elec-— - 
Moreover, it is impossible to experiment _ 
on evaporation on a sufficiently large scale in a labo- — 
trification. 
ratory. An infinitesimal amount of electricity may 
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SRS ae 5 
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