« ZurückWeiter »
Beccaria, Read, and others have shown that the state of moisture of the higher regions of the atmosphere is intimately connected with that of its electricity: a height of only six or eight feet above the surface of the earth is even sometimes sufficient for collecting powerful electric signs in an open situation. I have by means of a long wire, insulated on Mr. Singer's plan, when a copious dew was falling, collected pungent sparks when the height of the wire did not exceed five feet above the surface of the earth in any part of it. Hence it is concluded, that we cannot measure the electricity of the higher strata of the atmosphere until that of the lower, which may be excited by the evaporation or condensation of moisture, or by position, has been first measured. Now, if this. electricity of the lower strata could be proved to exist in a very small degree in closer situations, there would be no reason why it should not influence the column.
Mr. Read has, in my opinion, done much towards this by aid of the doubler.
The signs which the doubler produced were certainly strongly. analogous to those of his rod, and there are several other experiments which appear to me to prove that what is called the adhesive electricity of such like instruments is occasionally no other than that of the ambient air, which the peculiar structure is calculated to collect and display.
P.S.–Since writing the above, I have shown the tables to Mr. Singer, and was glad to find that he not only coincided in the conclusions drawn from them, but also in the idea that the electric state of the ambient air may be sufficiently powerful to influence the column : but I wished to ascertain the effect of heat upon a column not inclosed in a tube, as it might be objected that the air immediately in contact with the pile I used, and the inner surface, was not dried by the acid, although the hygrometric equilibrium might have been varied by heat. I therefore borrowed from Mr. Singer a pile consisting of 800 groups of zinc, silver, and paper, sup ported between three pillars of glass covered with sealing-wax, and placed in a very large receiver, together with an hygrometer, thermometer, and electrometer : the receiver was now placed over mercury, The divergence of the gold leaves was estimated as nearly as
1 could guess by the eye, and the following results were obtained :
minute June 3rd. 1
44 58 divergence 1.5 inch
Receiver taken off. 3 30
461 58 idem 3 37 receiver placed and acid introduced 4 37 323 593 idem
Time, b. m. 6 0
293 59 idem
32 56 divergence 1.25 inch
293 54 idem 10
Potash removed. June 6th. 11
35 53 idem June 7th. 0 0
a moistened card placed in receiver. June 8th. 11 30
40 50 divergence 1.25 inch
minute 3 45
1.5 June 9th. 9 another moistened card placed in receiver. June 10th. 6
42 60 divergence 1.25 inch
•5 There are several circumstances deserving observation in these experiments, but one in particular : viz., that on the 5th of June, when the air had been dried by a long continued action of the alkali, the power of the column was not increased by a rise of temperature in its usual degree. Possibly the discs of paper had been also deprived of a part of the moisture which appears necessary to the action of the column.
Hammersmith, June 10, 1814.
A Method of Measuring the Force of an Electrical Battery during
the time of its being Charged. By Lieut.-Colonel HalDANE.*
Let the battery be insulated, and at a small distance from it place an uninsulated electrical jar; also near to the jar place one of Mr. Cuthbertson's electrometers.
The electrometer being adjusted according to the degree of force which is intended to be employed as a measure of force to be communicated to the battery, connect the electrometer with the jar; make a metallic communication between the interior side of the jar and the exterior side of the battery, and connect the interior side of the battery with the conductor of an electrical machine.
Then, by the operation of the electrical machine, the battery receives a quantity of the electrical Auid, and becomes charged. The Auid which departs from the exterior side of the battery, is re
• From Nicholson's Journal.
ceived by the electrical jar, which also becomes charged; but this jar, being connected with the electrometer, explodes as soon as it acquires a force sufficient to put the electrometer into motion.
Now, the quantity of the electrical fluid which is received by this jar between each of the explosions, is a measure of the quantity of the fluid in the battery; and the number of explosions or discharges of this jar shews the number of measures which the battery contains, and consequently the force which it is capable of exerting when discharged.
Demonstration. The electrometer remaining under the same adjustment will require the same force to put it in motion : this force results from the quantity of electrical fluid received by the jar; and since it is admitted that when effects are the same, the causes of them must be equal, it is evident that the quantity of electrical fluid contained in the jar at the time of each explosion is the same.
It is also obvious that the sum of all these equal quantities of the electrical fluid which was contained in the jar at the time of each explosion, is equal to the whole quantity contained in the battery; for the battery being insulated the jar received all the electrical fluid which departed from the exterior side of the battery; and that quantity is said in the theory of Dr. Franklin) to be equal to the quantity in the interior of the battery.
Therefore it is manifest that the number of explosions or discharges of the electrical jar, is the number of equal measures of the electrical Auid which the battery contains.
But without putting too much confidence in any philosophical theories, the effects of this operation may be more satisfactorily shown by the following experiments :
Experiments. A piece of iron wire, about 0.045 inches in diameter, and about two inches in length, was placed in the circuit through wbich the discharge of a small electrical battery, which contains about six feet superficial of coated glass, was to pass.
The electrical jar employed as the measure of the charge of the battery contained about ninety square inches; and the adjustment of the electrometer was varied in each set of experiments, by changing the weight applied to the balance, and also the distance of the discharging balls.
Experiment I.—The electrometer being adjusted with its least weights, the discharging balls placed at the distance of one inch, and other parts of the apparatus arranged as before described, the electrical machine was put in motion, the battery and also the jar began to receive a charge, as was shewn by the repulsion of a pithball on a graduated quadrant placed upon the electrometer.
1. After the first explosion of the electrical jar, that is, after the battery had received one measure of the electrical Auid, a discharging rod was applied to complete the circuit in which the iron wire was placed ; but, upon the discharge of the battery, no change of appearance was visible in the wire.
2. The operation of the electrical machine being continued, the discharging rod, after two explosions of the jar, that is, after the battery had received two measures, was applied as before; but, upon the discharge of the battery, no change appeared on the wire.
3. The battery was then charged with three measures ; and upon discharging it as before, luminous particles of the wire were thrown off. 4. The battery, having received four measures, the wire, upon
the discharge, exhibited nearly the same appearance as before.
5. The battery, having received five measures, was discharged; the wire was red-hot, and separated.
6. The battery, having received six measures, was discharged; the wire was dispersed in red-hot globules.
The battery, upon receiving between nine and ten measures, made a spontaneous discharge.
Exp. II.-In the secoud set of experiments, the apparatus was arranged as before, and the electrometer adjusted with the same weight, but the discharging balls were placed at the distance of two inches. The results were, upon the discharging of the battery, after having received
1 No alteration in the wire.
5 ... Dispersed in red-hot globules. Between 7 and 8
A spontaneous discharge of the battery. Exp. III.- The apparatus being arranged as before, the electrometer was adjusted with its greatest weight, and the discharging balls placed at the distance of one inch; the results were, upon discharging the battery, after having received
1 No alteration in the wire.
4 ... Red-hot, and separated. 5 and 6 ... Red-hot, and dispersed in globules. Between 8 and 9 ... A spontaneous discharge.
Exp. IV.—The electrometer being adjusted with the greatest weight, the discharging balls were placed at the distance of two inches. The results were :
1. Luminous particles thrown off.
4 The wire was dispersed in red-hot globules. Between and 7 ... A spontaneous discharge of the battery.
Exp. V.-The apparatus remained as in the fourth experiment, with the addition of another battery, containing twelve feet of superficial coated glass, and the iron wire placed in the circuit of the discharge of this battery was about 0.08 inch in diameter, and two inches in length. The results were:
1 No alteration in the wire.
10 Dispersed in red-hot globules. Between 15 and 16
A spontaneous discharge.
HENRY HALDANE. Harley-street, May 27, 1797.
The electrical machine employed in these experiments has a glass cylinder of nearly 18 inches in diameter. It was constructed by Mr. Nairne, and is a most powerful instrument, particularly in exhibiting all the phenomena in which the negative, or electricity of the rubber is concerned.
An Inquiry into the Cause and Nature of Galvanism.
By Mr. James Milne.
SECTION I. From the great difficulties attending the theories of galvanism, by Davy, G. Lusac, Volta, and all others who are under the necessity of calling to their aid the assistance of attraction and repulsion, tuo occult qualities of matter, which may be said to have never been proved to exist, and of which we can form no idea of the manner in which they operate, I have been led to enquire whether a more simple and obvious property in bodies would not account for the whole phenomena, without having to call in the aid and operation of these unknown qualities of attraction and repulsion : and from the observations which I have been able to make in caresully reading over the whole experiments detailed in encyclopædias and other works, I am uf opinion that the theory which I have to propose will sufficiently account for all the actions exhibited by that interesting element, without the aid of attraction or repulsion.*
Let it be supposed that the galvanic fluid is one of a most subtle and elastic kind, like heat, of which it is supposed to be a modification; that it is of universal extent, and pervades all nature; that it is a compressing elastic fluid, and has a tendency from its own pressure, like all elastic fluids, to be forced into the pores of all other bodies, whether elastic, liquid, or solid, in which there is space for it to enter, and which, from their open nature they can no more pre
• The essay was written in December, 1833, and the author has had several corroborating proofs of the truth of the theory since that period.