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when the copper of the original is of a good quality. As soon as the galvanic plate has acquired the requisite thickness, and the parts grown over the edges of the original are filed away, it springs loose of itself, without any further trouble. It hardly need be mentioned, that a casting of gypsum would answer all the purposes of copper plate, provided it were nicely managed, and taken from an original engraving that was not under-cut.
(To be continued.)
On Voltaico-Electric Quantity and Intensity. By Dr. Buff. (Ann.
der Pharm., t. 32, p. 1.*)
The author has had in view the study of that species of mysterious property which Faraday conceives to be found in voltaic electricity, by virtue of which it is more easily transmitted ; a property which he has named intensity, and which he distinguishes from quantity. He has found that this property is, as I have already indicated, only an effect of conductibility, by virtue of which the neutralization of two electricities accumulated at the poles of the pile is more or less easy.
The experiments of Dr. Buff are not all new, but they are interesting, as they confirm those which have already been made on the same subject by other philosophers.
He arrived at the conclusion, by varying the number of pairs in a pile, that if the circuit is closed by an imperfect conductor, the facility which this possesses of transmitting the quantity of electricity which can be developed by the battery is universal in proportion as the number of pairs is augmented.
The effects of tension observed by Dr. Buff are more numerous and more remarkable. He has at first studied them on a pile, the poles of which were insulated. The centre pair gave the same tension as it possessed when alone; two pairs, apart from the middle of the pile, gave a stronger tension; three, a still stronger ; and so on to the poles, where the electricity attains its maximum. The author appreciated the electrical state of each pair in diverse manners, and in particular by means of a copper wire soldered to zinc, which he put in contact with the inferior plate of the condensor, whilst he touched the superior one with the finger.
By making the poles communicate with each other by distilled water, the same distribution of free electricity in the pile has been found, only it was a little more feeble. With acidulated water placed between the poles, and which was decomposed, the electricity of tension was still found in those pairs nearest to the poles. But no portion of it could be found when the poles had been metallically united.
*Archives De L'Electricitie, No. 1.
The same effects have been obtained by charging the pile with diluted sulphuric acid, in place of ordinary water. By reuniting the poles by distilled water, the tension was still feebler, and no decomposition took place in any part; but when reunited by acidulated water, decomposition took place in all parts, in the troughs of the pile, as well as in those into which the poles were inserted. The tension has in all cases been stronger at the poles.
The author remarks the analogy which exists between these effects and those of an ordinary electric battery, charged with electricity from a machine ; and he thence concludes that the greatest tension, or the static intensity of the pile, only proceeds from the resistances which the circulation of the electricity meets with. We conceive, then, that it is at its maximum at the poles, and that, without being obliged to attribute to the current a mysterious property, there exists for the two electricities, accumulated at the two poles, a tendency to neutralization, more or less strong, and consequently a greater facility for the current which results from this neutralization to traverse the imperfect conductors.
On an Advantageous Manner of Constructing Grove's Pile. By
C. A. Gruil. (Ann. der Physik, tome li. p. 381.)* The author at first constructed this pile by placing a cylindric ring of platinum, in a porous earthen tube, closed at its lower extremity, and filled with nitric acid. The porous tube was introduced into a cylindrical jug, filled with diluted sulphuric acid, in which was also inserted a cylinder of amalgamated zinc, which enveloped the tube without touching it. This piece of apparatus, which is almost similar to a calorimeter, gave powerful results, but it presented this inconvenience: the thin layer of nitric acid, comprised between the surface of the cylindric ring of platinum and the interior partition of the porous tube, became rapidly heated, entered into a state of ebullition, and emitted nitrous vapours.
The author then substituted, for the cylindric ring of platinum, two plates of the same metal, cutting each other at right angles, following the axis of the tube, and forming a cross.
He has, even at a later period, added a third plate, in such a manner that the three plates crossed each other at the axis, by making angles of 60° with each other. They were thus disposed around the axis, like the leaves of an open book round the back of the book.
After this disposition, all the nitric acid being in the circuit was much less heated. This pair would act during several hours without any disengagement of gas or decrease of the force of the current, when even the nitric acid had taken a deep green colour.
Archives De L' Electricitie, No. 1.
A Register of the Electric State of the Atmosphere, in relation to its
Meteorological Phenomena, for the Month of June, 1841. By W. H.
Time in hours and minutes.
| Day of month.
74 29.90 mere Mountainous mass- positive An occasional, low current,
causing slight divergence
until 2 P.M.
N.V. and there cirrose
breeze. mulus cloud.
positive Remarkably steady divergence
until the approach of sunset.
divergence, and frequently
casional intermission of a
proach of a ragged cumulus. 11 a.m.
Hasty, showers of negative Streams of moderate sparks
from terminus. 11,9 a.m.
positive Increased energy of electric
current for the space of an
gold leaves. 1, 20 p.m.
Hail shower. positive Torrent of brilliant sparks.
during the showers, Dega-
tive; with a strong positive
current in the intervals.
stances only, during a few
Hazy upwards, with neutral Cynanche tonsillaris, frequent slight, n. little fine rain at
among children and young by E. times.
persons 58 29.65 faint Thickly clouded. neutral
light Veil of cloud rapid-positive The electroscopes diverge breeze ly dispersing,
during morning only, — dis
tant lightning at eve.
variable clouds, at great
breezes, difications of cir-
S. by W. thery cirri.
positive Free and continuous electric to S. E.
6, 10 p.m. 6,25 p.m.
light Blue sky, with cir. positive Free divergence. breezes, rose fibres dis
E. by N. persed abroad. 2 p.m. 66 29.40 S. by W. The cirrose fibres All divergence has ceased.
have gradually re-
tions of cumulus.
Time in hours and minutes.
5 Day of month.
and cations of clouds.
19 2 p.m. 66 29:32 light Thunder from negative Waves of electric fluid rush breezes, clouds distant
through the apparatus subW. about a mile.
sequent to each successive
lightning-flash. 12, 20 p.m.
Rain in abundance. positive Current of small sparks.
No further trace of elec. action. 20 164 29.50 strong at Densely clouded. neutral
times, W.S.W. decreased Continued gentle neutral Numerous cases of odontalgia.
66 29.60 sudden Occasional gentle neutral
neutral Sensation of langour and mus
cular relaxation very general. 22 66 29.65
Clouds and thin neutral zephyrs haze beneath.
W.S.w 1,25 p.m. increased Hasty dispersion of positive Slight divergence of electroto smart clouds, except fine
scopes immediately on disbreeze, cirrose fibres, here
persion of clouds; increasing S.W. and there.
for one hour, becoming uni
form, and ceasing at sunset. 23 64 29.50
Blue sky and mo- neutral Odontalgia, rheumatism, and difications of cir
various neuralgic affections rus alternately.
Clear blue sky. neutral 2 p.m. 66 29.40
smart Few modifications positive Free divergence immediately breeze of cirrus cloud.
on rising of the breeze. has just sprung
The most delicate test-instruceased continued rain by
ments fail to detect any free night.
electricity. All the lastnamed diseases are increased: extreme langour of the animal
system prevails. 25
64 29.30 scarcely Continued gentle neutral
from S.E. 11,30 a.m.
breeze, Fair with flocculent neutral
Blue sky with cu- neutral
2,30 p.m. 67 29.45 slightly Nimbus flying has- negative Free divergence when a nimabated tily over.
bug reaches zenith of appa
decreased Numerous modifica- positive Slight divergence steadily. to a smart tions of cirrus.