form of the stereoscope had ever made its appearance. I now, however, take the very earliest opportunity of making the acknowledgement, and hope you will be able to give it a place in your forthcoming Number.

I am,

Gentlemen,

Respectfully,

Edinburgh, Feb. 10, 1857.

JAMES ELLIOT.

ON INDUCTION.

BY A. MASSON.

The object of these experiments is to establish the truth of the following facts, upon which the whole theory of induction reposes :1. All electrical currents, whatever be their tension, produce the same phænomena of induction.

2. The induced currents of different orders are composed of two systems of currents equal in quantity, but possessing different intensities. (To assimilate voltaic currents to the discharges of Leyden batteries, the two secondary currents produced by the rupture and establishment of the primary current, must be taken.)

3. The currents which have the highest tension are direct for the secondary current, and inverse for the currents of other orders.

4. The physiological and magnetic effects of the currents, as well as the elevation of temperature, are produced by instantaneous actions, which only depend on the quantity of electricity and the tension of the current, and by no means on the duration of its action. The quantity of chemical action, the total heat evolved in a circuit, and the deviation of a galvanometer, are independent of the tension and time, and remain always proportionable to the total quantity of electricity set in motion.

Voltaic induction.-The secondary current of Ruhmkorff's apparatus decomposes water abundantly by the employment of poles composed of very fine platinum wires placed in tubes of glass, to one extremity of which they are soldered; these wires dip into the fluid 1 or 2 millims., and the gases disengaged at each pole form a very pure detonating mixture.

The galvanometer remains stationary, or undergoes oscillations due to the double current; by producing a spark in the induced circuit, one of the currents is nearly destroyed; the decomposition of acidulated water becomes polar, and the deviation of the galvanometer is certain; like the voltameter, it indicates a direct induced current.

A tertiary current gives a detonating mixture; it has no action on the galvanometer. I have not been able to procure an apparatus capable of producing a spark for the tertiary voltaic current. I hope soon to be able to operate upon the currents of different voltaic orders, as upon the secondary current.

Induction by the discharge of batteries.—I charge a condenser by the Ruhmkorff's apparatus, employing the precautions indicated in my Etudes de Photométrie électrique; I then obtain a primary current formed of successive discharges sufficiently close together to give the effects an apparent continuity. The circuits disposed

for the induction are formed of flat spirals, of which the wires are perfectly insulated. I stopped at the induced current of the fourth order, as I only had three pairs of spirals.

The induced currents of all the orders decompose water and furnish detonating mixtures at each pole. The galvanometer remains stationary. The re-electrometer of Marianini undergoes continual perturbations in consequence of successive magnetizations and demagnetizations.

By producing a spark in the circuit, either by means of an electromicrometer or of the electrical egg partially deprived of air, water undergoes a polar decomposition; the galvanometer acquires a permanent deviation, the re-electrometer receives a fixed magnetization, and these three pieces of apparatus always act concordantly, whatever be the direction of the primary current, which may be changed at pleasure by the commutator of Ruhmkorff's apparatus. The induced currents might be extended far beyond the fourth order, and made to produce a continual series of sparks.

The re-electrometer, the indications of which have always appeared to me to be perfectly certain in the numerous experiments in which I have used it, was employed to find the direction of the currents induced by discharges of batteries charged by an ordinary electrical machine, taking care that the spark of the induced circuit was at the maximum striking distance; the ingenious instrument of M. Marianini leaves no uncertainty, and all the currents of different orders produced by strong discharges showed the directions which had previously been found for weaker currents.- Comptes Rendus, Dec. 15, 1856, p. 1115.

OBSERVATIONS ON THE ZODIACAL LIGHT AND ON SHOOTING

STARS. BY PROF. HEISS*.

At the recent Meeting of German Naturalists at Vienna, Prof. Heiss of Münster (Westphalia) gave the results of his observations on zodiacal light (with reference to Prof. Argelander's memoir on the same subject).

The first notice of zodiacal light was published, about 200 years ago, by Dominic Cassini; a more exact investigation has been undertaken in recent times by Baron von Humboldt. The phænomenon is generally difficult to observe on account of its want of conspicuousness; at certain periods, however, as was the case in the spring of 1856, it becomes more intense, somewhat resembling a distant fire, Most authors state that the zodiacal light is visible only during certain periods of the year; Prof. Heiss, however, after 200 observations, has found that it is visible during the whole course of the year. In summer the protracted twilight is an obstacle to the observation, but the presence of the zodiacal light may be precisely inferred from the form of the crepuscular light. The determination of the limits of zodiacal light requires particular care: the lower southern margin of the pyramid is generally the less distinct.

Prof. Heiss exhibited a map showing the shape of this light, as * Communicated by the Count Marschall.

determined by a series of observations. The variations in its intensity probably depend on atmospheric changes only. Prof. Heiss expressed his desire that further observations should be made, and proposed, as a problem still requiring solution, the question whether the phænomena of zodiacal light observed at different stations are not really different from each other. The phænomenon may be alike perceived in the evening and in the morning; e. g. on February 3, 1856, when in the evening the light was very conspicuous in the western part of the firmament, and appeared again, nine hours later, in the eastern part; its figure being an ellipse with a major axis of 116°, and a minor axis of 33°. It has not yet been possible to observe the polarization of the zodiacal light on account of its feeble intensity.

Prof. Heiss pointed out the desirability of corresponding observations on the aurora borealis, especially for determining the distance of these two peculiar lights. He himself had made the so-called "rays" of the aurora borealis a particular subject of observation, making use, for the grouping of the results, of diaphanous maps to protect the eyes against the excessive intensity of the light. The aurora borealis is known to be visible at great distances; e. g. the same phænomenon was observed by Prof. Heiss at Aix-la-Chapelle, and by M. Schmidt at Naples. Although the last aurora boreales were very feeble, there is no reason to suppose a general diminution of the phænomenon, or the beginning of a period of periodical decrease.

Prof. Heiss has observed the phænomenon of falling stars continuously since 1849, during the whole course of the year. The results of his observations have been graphically represented on wooden tables of a peculiar construction, and so placed that they exactly answer to the region of the firmament actually before the eye of the observer. Falling stars observed at the same time at different places are not always identical; they may be distinguished from each other by means of several geometrical constructions. The igneous globular meteor of February 3, 1846, was seen at places very distant from each other. According to Prof. Heiss's observations, it took its origin at a vertical height of 30 German (about 150 English) miles above the St. Gothard, it progressed towards the north of France and disappeared above Chalons, passing through a distance of 54 German miles within the space of a few seconds. Another igneous globe was seen in August 1856 at Brussels, Namur, and other places; first appearing at a height of 10 German miles near Namur, and disappearing at a height of 3 German miles: its real diameter was 300 Paris feet.

Prof. Heiss expressed a wish that notice might be given him of any phænomena of this kind wherever such may have been observed, and stated that his own observations on falling stars did not fall far short of 9000.

PROFESSOR SCHOENBEIN.

We have the satisfaction of recording, that the King of Bavaria has presented a gold medal, accompanied by a prize of about 3500 francs (£140), to M. Schoenbein for his investigations on ozonized oxygen.

ON THE INFLUENCE EXERCISED ON THE MAGNETIC NEEDLE by
MUSICAL STRINGS IN A STATE OF RESONANCE.
REINSCH*.

(Extract.)

BY DR. H.

The interesting experiment of the rotating copper disc instituted by Arago, led me to examine the effect upon the magnetic needle of a vibrating string covered with copper wire. For this purpose I stretched a copper-covered string upon a violin, and suspended above it a light magnetic needle by means of a filament of Cocoon-silk. The needle that I made use of was a sewing-needle, about an inch and a half long. The direction of the string was made to coincide exactly with the magnetic meridian, and the distance between the string and the needle was about the twelfth of an inch. The string was now thrown into the state of resonance by means of a violin-bow, but the needle remained entirely motionless; on the contrary, it rather appeared that, after having been made to oscillate purposely, it returned more rapidly to its normal direction than if the string had been allowed to remain mute. Instead of using a metal string I now had recourse to one of catgut, and suspended the needle above an ordinary treble violin string, when the first stroke of the bow was sufficient to impart a considerable deflection to the needle, and by five or six strokes in quick succession a deflection amounting to 90° is easily produced. The purer the tone is, and the greater the tension of the string, the more marked is the deflection.

"The various deflections, corresponding exactly with those brought about by the galvanic current, are exhibited in the subjoined figure.

"The string, a b, is made fast at f; br is the bridge of the violin ; n the magnetic needle freely suspended; st indicate the stroke of the bow, its direction being shown by the arrow-head. Immediately that a stroke of the bow is given near the bridge in the direction shown in the figure, the needle is deflected westward, as seen at 1; on giving the stroke in the contrary direction, as shown at 2, the needle is deflected in an easterly direction; on giving the strokes at the south end of the needle, the deflections take place in exactly opposite directions to those brought about by the strokes given at the north end of the needle, as seen at 3 and 4."

* Ueber den Einfluss tönender Saiten auf die Magnetnadel, von Dr. H. Reinsch. Communicated by W. G. Lettsom, Esq.

ON ELECTRICAL HEAT.

To the Editors of the Philosophical Magazine and Journal.

GENTLEMEN, In the Philosophical Magazine, vol. xii. p. 553, Sir W. Snow Harris has continued his opposition to an established law of electrical heat, without, as is necessary, describing minutely the experiments which he considers irreconcileable with that law. It is therefore impossible to assign a reason for the remarkable result which his experiment with two Leyden jars of different sizes led to. If Sir William did really, as he asserts, charge the two jars with the same amount of electricity, and all other conditions in the two jars were identical, the small jar would undoubtedly on its discharge have caused a stronger heating effect of the wire than the large jar. At the same time the theory of the Leyden jar teaches that this experiment can by no means serve as an accurate test of the law in question, and cannot be called a crucial experiment. May I be allowed in conclusion to repeat a statement which is not expressed with sufficient clearness in my last letter? I request the reader not to consider objections to my researches as well founded because I leave them unanswered; I pass over objections which are based upon a misconception of my statements, and are easily corrected. I have the honour to be, Gentlemen,

Yours truly,

Berlin, Jan. 20, 1856.

P. RIESS.

ON THE SPIRALITY OF MOTION IN WHIRLWINDS AND TORNADOES.

BY W. C. REDFIELD*.

1. An aggregated spiral movement, around a smaller axial space, constitutes the esential portion of whirlwinds and tornadoes.

2. The course of the spiral rotation, whether to the right or left, is one and the same in this respect throughout the entire whirling body, so long as its integrity is preserved. But the oblique inclination which the spiral movement also has to the plane of the horizon, is in opposite directions as regards the interior and exterior portions of the revolving mass. Thus, in the outward portion of the whirlwind the tendency of this movement is obliquely downwards, when the axis is vertical; but in the interior portion, the inclination or tendency of the spiral movement is upward. This fact explains the ascensive effects which are observed in tornadoes and in more diminutive whirlwinds.

3. Owing to the increased pressure of the circumjacent air in approaching the earth's surface, the normal course of the gradually descending movement, in a symmetric whirlwind, is that of an involuted or closing spiral; while the course of the interior ascending movement of rotation is that of an evolved or opening spiral. Hence, the horizontal areas of the higher portions of the whirl exceed greatly those of its lower portions.

4. The area of the ascending spiral movement in the vortex, as it leaves the earth's surface, is by far the smallest portion of the * Read before the American Association at Albany, Aug. 26, 1856.