Mario Giardini to Faraday   24 March 1856¹

Naples 24th March 1856.

Sir

A discovery which must interest you, as it relates to the application of the terrestrial magnetism alone to Set in motion a magnet of great magnitude to produce such currents as to show brilliant sparkles, intolerable electric shoke, and the quik discomposition of water. This magnet may active the electric Telegraphes; for I have demonstrated that its energy follows the ratio of the masses of iron, which are used with the corrispondens of multiplicators. It would be interesting to me to learn your opinion, Sir, concerning the explanation of the strange phenomena physical - chimical - physiological, which are excited in a temporary magnet from the terrestrial magnet alone. The apparatus is identical to that of Clark; it only differs from it in the dimensions. It consists of 3. bands of iron wire twice made red hot, of the diameter of 2. milimetres, and 1. meter and 12. centimetres long: each weing 18. chilogrammes: the 3d bent in the shape of a horse shoe, so that the straight points remain distant from each other 95. centimetres: 4. Tubes are placed at hard friction: 2. in the whole length of the long bands, and 2. in those which are supported by the bending band, which will act as anchor of the magnet. Over it others identical are there placed to a light rubbing, to be easily taken away when requisite. Around the circumferences of these 2. tubes, circular brass fenders are to be salded. To the whole length of the fenders, place 7 rows of spirals of copper wire of 2. millimetres and half diametre, covered with cotton ribbands wet in a solution of gum lack. On a fitted apparatus they are placed parallel to the horizon, and 25. centimetres distant from each other, and their extremities free are opposite to the ends of the 2. iron [m]asses of the 2. multiplicators. In each ball are involved 1000. metres of Copper wire, covered with Silk a millimetre diameter. The multiplicatory with a fit engine may wheel rapidly almost in contest with the free extremity of the magnet, while the oppostie ends are brought in contact with the bending band. It must be observed that the phenomena do not fail taking away the anchor. After keeping these magnetic bands one month between the magnetic poles of the earth, without the spirals, they are seen lightly magnetized so as to draw the end of a very thin iron wire, holding in the fingers the opposite end. By giving rotatery motion to the multiplicatory the band shall not only attract more strongly the iron wire, but shall hold it in adherence to them, and others much heavier shall be attracted by the same bands: but acting the rotation of the multiplicators both wires drop. This experiment shows that during their motion, the magnetisation of the bands increases: and to demonstrate with more evidence it is sufficient to place 2. magnetized needles suspended into the inside of 2. crystal balls, and adapted to the ends of one of the bands, shall readly show that their ends are magnetized with bipolar-magnetism, and shall place themselves parallel to the direction of the band. By the rotatory motion of the multiplicators the needles shall incline towards the same band, which shows the increase of its magnetization: at the end of the rotation of the multiplicators the needles shall resume their former position. Placing a torpid Galvanometre to a needle within the circuit of the currents of the bare bands, making use of balls having 600. metres of copper wire involved each of the diametre of 2. millimetres, covered with silk, in one half rotation of it the needle discribes an arch of 10. degrees, setting in action those of tension the needles scarcely deviating of a few degrees. Whether employing the multiplicators of tensions, or those of quantity none of the 3. phenomena appears. Placing the spirals in the 3. bands, and giving action first to the long ones with the multiplicators of quantity, and placing within the circuit the Galvanometre, in one half rotation of the balls, the needle describes an arch of 110. degrees. It is surprising to observe that the spirals having their ends free in the air, or joined to the close circuit the galvanometre being in communication with the little cups of mercury, double compartment, the direction of the needle shall also be of 110. degrees. How can this phenomenon be explained? It must be acknowledged that the magnet being in the magnetic ambient, the disquilibrium induced by the extremely high magnetism of positions of the bands, determines the absorption of the of magnetism of the same ambient by the free ends of the spirals: or when these are joined to the close circuit for it is impossible, that the high magnetism of the bands, which causes the needle to deviate 10. degrees could excite a current introduced into the spirals, to cause the galvanometre needle to discribe an arch of 110. degrees: and it is known that in the temporary magnetic moved by the Voltaic Pile, the current enters through the ends of the spirals, magnetising the iron, round which it revolves: likewise the terrestrial magnetism derives from the external part of the spiral on the iron wire bands to magnetize it energetically absorbing it, whether through the free ends of it, or through its mass when disposed in close circuit.

Phenomena which appears in the apparatus set in action.

The sparkle is observed as well in the brass commutators as in the paring disks in which splits are cut on the front face of it, when they are placed in the axes of r[ot]ation, and fixing the end of a copper wire in the hole through the plate of the hoele, while the opposite end already sharpened opposite to the splits of the brass plate, wheeling the multiplicators, the sparkles appears, and in Various lines according to the metal used. In the mercurial apparatus the Sparkle is extremely brilliant and constant, and by placing in the circuit the flat spirals 400. metres long becomes even more brilliant, placing in the circuit of that current 6. masses of coals being 100. kilograms each, residue of the distalation of the coal the sparkle will be more and more brilliant.

The shoke and the decomposition of water shall be obtained as in Clark’s apparatus: exceedingly strong, and almost intolerable is the former, most distinct the latter: and these phenomena are observed nearly with the same intensity, bringing the magnet into the various arimists on the horizon, and what is more wonderful even being perpendicular to the plane of the magnetic meridian. The magnet is equally active when placed perpendicularly to the horizon near the multiplicators - hence I feel more convinced that absorption of the terrestrial magnetism on the bands of the spiral excited the disquilibrium caused in the one, and in the others from the currents of the magnetism of position of the bands, at the moment of the rotation of the multiplicators be the true cause of so singular phenomena: therefore it shall not be strange to assert, that as the electric machinery desires upon its Conductor the statical electricity of the earth, so to the temporary magnet flows the dinamical electricity from the earth itself.

And when you, Sir, have granted approbation to these theorical conceits I can freely tell to the european Physicians conform yourselves to my theory, because the first physician of our ages, Farad[a]y, agrees with me.

Pray, Sir, honour me with a speedy answer | while I am | Your most obedient Servant | The Physical Professor of the | Neapolitan V. University | Mario Giardini

Address: À Monsieur | Mr. le Profr. Faraday | à | Londres