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POPULAR SCIENCE REVIEW. 
compared with the “syren” of Cagnard de la Tour, or with the toothed wheel 
of Savart. By these means, especially when combined with improvements 
suggested by M. Zantedeschi, the stability of the note, or the amount of its 
error, may at any time be ascertained. In France, the A has been lowered 
from 890 to 870 vibrations. 
Zantedeschi does not appear to be aware of investigations of, and the 
beautiful instruments for, determining the vibrations of a note, invented by 
Professor Wheatstone. 
Actinism; or Chemical Bays. — M. Niepce de Saint Victor has been 
zealously continuing his researches on the absorption of the chemical principle 
of the sun’s rays. He gives a very instructive result in proof of this absorb- 
tion. An unglazed piece of porcelain ( bisque ) is exposed to sunshine, one-half 
of it being protected from solar influence by an opaque screen ; it is then 
taken into a dark room, and a piece of photographic paper is placed above it. 
This paper is blackened over all that part which is opposite to the solarized 
portion of the porcelain, whereas no change is produced upon that division 
which corresponds with the unsunned part of the plate. 
ELECTRICITY AND MAGNETISM. 
Musical Sounds produced by Electricity. — Mr. George Gore has devised the 
following beautiful experiment : — 
A circular pool of mercury, from one to three inches diameter, is formed 
in a circular vessel of glass or gutta-percha ; this is surrounded by a ring of 
mercury about one-eiglith to one-tenth of an inch wide, and both are covered 
to the depth of about half an inch with a rather strong solution of cyanide of 
potassium. The pool of mercury is then connected by a platinum wire with 
the positive pole of a powerful voltaic battery, and the ring of mercury is 
connected with the negative pole. 
The connection being completed, the ring of mercury becomes covered with 
crispations or elevated sharp ridges, about one-sixteenth of an inch asunder, 
all radiating towards the centre of the vessel, and a definite or musical sound 
is produced capable of being heard, on some occasions, at the distance of 
forty or fifty feet. The loudness of the sound appears to depend greatly on 
the power of the battery. If the battery is too strong, the sounds do not 
occur ; and they are prevented by using the solution of the cyanide in too 
concentrated a state. 
Magnetism.— Professor Wiedemann has been engaged in an inquiry on the 
relation between the magnetic and the mechanical properties of iron and 
steel. Amongst many exceedingly curious results, he has obtained the 
following : — 
If an iron wire be twisted during or even after the passage of a voltaic 
current through it, the wire becomes magnetic. When the wire is twisted 
in the manner of a right-handed screw, the point at which the current enters 
becomes a south pole ; in the opposite case it becomes a north pole. If, 
during the passage of the current, the wire be twisted in different directions, 
the polarity changes with the direction of the twist. If twisted in different 
