by Nobili, of a vivid light, produced when a Leyden jar is discharged through a flat spiral.

The foregoing views are not presumed to be given as exhibiting the actual operation of nature in producing the phenomena described, but rather as the hypothesis which have served as the basis of my investigations, and which may farther serve as formulæ from which to deduce new consequences to be established or disproved by experiment.

Many points of this subject are involved in an obscurity which requires more precise and extended investigation; we may, however, confidently anticipate much additional light from the promised publication of Mr. Faraday's late researches in this branch of science.

LIII. Method of increasing Shocks, and Experiments with Prof. Henry's apparatus for obtaining sparks and shocks from the Calorimoter. By C. G. PAGE.*

Dear Sir,

Salem, May 12, 1836. TO PROFESSOR SILLIMAN,

I have lately constructed an apparatus for obtaining shocks from the Calorimoter, which has furnished some curious results; and as you may, perhaps, deem them worthy of publication, I send you herewith a sectional drawing of the apparatus, with a description.

Fig. 80, Plate X. represents a section of an apparatus for obtaining shocks from the Calorimotor. The coil of copper ribbon, contained in the box B, Z, is 220 feet long, an inch wide, and has but four solderings or joints throughout its length. The separate lengths of 55 feet each are cut from single sheets of copper. This is easily done by cutting the alternate strips within half an inch to the edge of the sheet, and then bending them one upon the other, to bring them in the same line of length; in this way the integrity of the circuit is better preserved than by numerous solderings. The ribbon is wound with single strips of list intervening. On five of the coils at distances indicated by the figure, are soldered strips of copper which pass through the cover of the box and are then bent down to receive the thimbles for the mercury. This forms a convenient arrangement, as the mercury cups are easily emptied by straightening the copper strips. t represents the copper tube with a curved strip of copper soldered to its

* From Silliman's Journal, for Oct., 1836. This number of Professor Silliman's excellent Philosophical Journal, did not arrive in London till after Christmas last.

extremity for dipping into the mercury cups.

For the sake

of brevity in detailing the experiments, instead of the copper tube of right or left hand, merely the words right and left hand will be used: and by the abbreviation, neg. con. and pos. con. will be understood the strips of copper connecting the cups with the negative and positive cups of the Calori

motor.

On putting the pos. con. into cup 1, and the neg. con. into cup 2, a bright spark and sharp snap are produced, when either of the connectors is raised from its cup. When the neg. con. is raised from cup 3, the spark is more brilliant than the last, accompanied with a louder snap.

When the neg. con. is raised from cup 4, the spark is more voluminous, but not so intense as the last named, nor is the snap so loud.

When the neg. con. is raised from cup 5, the spark is still less bright, and the snap less loud.

When the neg. con. is raised from cup 6, (220 feet) the spark and snap are both feeble, even when compared with those given by cup 3. It would seem then from these results, that the limit of intensity is attained at cup 4, which gives a length of 110 feet; but this inference is somewhat weakened by the following facts. The shocks by no means obey the same law; the maximum being obtained by immersing the copper tubes in cups 6 and 1. 6 and 1. For convenience of arrangement, suppose the positive connector is in cup 1, and the right hand in cup 1. The left hand is to pass along with the neg. con. into cups 2, 3, 4, 5, and 6, and as con. is raised from these cups successively, the shock increases, and from cup 6, is a maximum with this apparatus. It will be seen from this, that from cup 4 to 6, the shock is inversely as the spark, while in the first half of the coil, it is in the same ratio. It may be well to mention here, that I found if the surface of the mercury, where the contact is broken, be covered with water, the shock is very much increased. The rationale I am unable to give, but such is the fact. This augmentation does not take place at every rupture of contact, but is best attained by striking the connector against the bottom of the cup and quickly raising it. The shock is also increased by covering the mercury with naphtha and the mercury appeared to be oxidized, the naphtha soon growing turpid.

The next results to be stated are still more curious, and according to the received theories of electro-motion, difficult to explain. The pos. con. and right hand are still in cup 1.

The neg. con. in cup 2, and the left hand in cup 3, the shock is now stronger than when the left hand was in cup 2 with the connector, and goes on increasing as the left hand is carried into cups 4, 5, and 6, in succession.* Let now the pos. con. and right hand remain in cup 1, place the neg. con, in cup 3, and the left hand in cup 4, the shock goes on increasing as before, and when the left hand arrives at cup 6, the shock is as strong as that obtained from the whole coil (220 feet), while the actual circuit from positive to negative is only 80 feet. Let pos. con. and right hand remain in cup 1, put the neg. con. in cup 4, and left hand in cup 5, the shock is now as strong as when the whole coil is in the circuit, and when the left hand is in cup 6 the shock is stronger than can be obtained from the apparatus in any other way. These last results prove that the real maximum as indicated by the shock, is given by the direct circuit from positive to negative, through half the coil, with the lateral co-operation of the other half.

Thus much being known, we might reasonably expect that while the connectors are in the extreme cups 1 and 6, we should obtain shocks from any two intermediate cups, and this I found to be the case; but, contrary to expectation, I obtained shocks from cups entirely without the actual circuit. For instance, the pos. con. in cup 1, neg. in 3, right hand in 4, and left hand in 6. In this case the shock was slight; but by thrusting needles into the thumb and fore finger of the left hand, and immersing the needles in cups 4 and 6, the shock was extremely painful.

Again. Solder the copper tube of the left hand to the neg. con., put the pos. con. and right hand into cup 1. When the end of the neg. con. is raised from cup 4, no shock is felt, but when the other end is raised from the cup on the battery, a shock is felt. Other things remaining the same, carry the right hand from cup 1, out of the direct circuit to cup 6. Nearly the reverse of the last named phenomena takes place. A strong shock is felt when the end of the neg. con. is raised from cup 4, and a weaker one when the other end is raised from the cup on the battery. This experiment appears still more striking, when the right hand is carried into the same cup with the neg. con. cup 4: a shock is felt, although the distance by the direct circuit from hand to hand is only about eight inches. Having detached the copper tube from the connector, put the pos. con. in cup 1, the neg. con. in cup 4, the right hand in cup 4, and the left hand in the neg. cup on the bat

* An assistant is necessary to make the immersion of the connectors.

tery. It is immaterial now which end of the neg. con. is raised, both producing a shock. If the right hand is now carried to cup 6, the shock is a maximum.

A direct shock cannot be obtained from this instrument. To test this, I passed fine needles deep into the thumb and forefinger of the left hand, and immersed them in cup 6 and the negative cup on the battery, the positive con. being in cup 1; no shock was felt on breaking or making circuit.

If a file or rasp be inserted into either of the cups and the connector drawn across it, the shocks become insupportable from the rapidity of succession. The scintillations from the file in this case are very beautiful, being by far the most brilliant and copious in cup 4. Very pleasing effects are produced by breaking the circuit with a revolving spur wheel, A little spur wheel of copper is so made that, in revolving, one spur shall leave the mercury before the next touches. In this way a rapid succession of sparks and detonations are obtained. If bits of silver leaf are hung upon the spurs as the wheel revolves, the combustion of the silver leaf is very vivid, burning with its peculiar emerald light. The shocks produced while the wheel is revolving are very disagreeable.

The decomposition of water was easily effected by breaking the circuit under its surface with two clean strips of copper. On using two small platinum wires, they adhered as with a deflagrator.

The coil was tried with a two-quart Leyden jar, and shocks were obtained from cups entirely without the direct circuit. I refrain from stating other results with the Leyden jar, as they must be rendered somewhat equivocal, by the imperfect insulation of the coils.

It may also be worth mention, that by using the needles as before, I obtained with this apparatus, shocks from a single pair of plates only four square inches (single surface). We have then in this instrument a battery by itself, from which shocks of all grades can be obtained, and in cases of the medical application of Galvanism, it must prove far more convenient than the ordinary methods.

POSTSCRIPT.

Salem, June 8, 1836. One of the most pleasing experiments with the coil, is breaking the circuit with a revolving spur wheel. In former experiments, I produced the revolution of the wheel with a string, as in the wheel tinder box, having failed to effect it with a magnet. But I have since invigorated my calorimotor, by removing and cleaning the zinc plates, and a small horse

shoe magnet is now sufficient to produce rapid revolutions, with the most brilliant results. The circuit in this case is terminated in cup 2, as the rotations diminish in proportion to the length of the coil used. The wheel is fitted with a wooden stand and trough, precisely as for magnetic rotation. The deflagration of the mercury is extremely vivid, giving copious fumes. If the experiment is performed in a dark room, it exhibits in a superb manner the well known optical illusion, of a wheel in rapid motion appearing to be at rest. As the wheel is illuminated by a rapid series of sparks, it does not appear to be exactly at rest, but exhibits a quick vibratory movement. I have before alluded to the nature of the shocks given by the wheel, but with this self-regulating apparatus, an assistant can be dispensed with, and shocks of any duration and degree can be obtained, by immersing the copper handles as before directed. The strongest shock being obtained by immersing the copper handles in cup 6, and the negative cup of the battery. This last experiment is difficult to explain. The left hand being in cup 6, it is immaterial whether the right hand is carried to the positive or negative cup on the battery: a strong shock is felt in both cases, but that from the negative cup is somewhat stronger, and is the real maximum, if the circuit terminates with half the coil.

Explanation of the Phenomena, &c.

Mr. Page's variations of Professor Henry's original experiments are very important; but as that gentleman has not ventured an explanation of the cause of the phenomena, it may perhaps be interesting to many of our readers to know that the whole may be explained upon the theoretical principles already placed before them. In every instance the phenomena may be traced to the collapsion of the electro-magnetic lines. In some instances the phenomena proceeded from a primitive current; in others, from a secondary current; and in others from both primitive and secondary.

When the battery circuit embraced portions of the coil between 1 and 2 ;-1 and 3;-1 and 4; the remaining part of the coil, as far as the left hand enclosed it, became the circuit for a secondary current. When the battery circuit embraced half of the coil; or from 1 to 4, the other half, when the left hand was in 6, was traversed by a secondary current, every time the battery connexions were broken. When the battery circuit embraced the 'coil from 1 to 3, and the hands in 4 and 6; the shock felt was entirely from the secondary current of that part of the coil immediately between the hands.