Moritz von Jacobi

“ We must not lightly abandon conclusions founded on the nature of things, and those to which I refer are drawn solely from the integral , expressing the magnetic attraction and supposed to be independent of the speed. Besides, it rests upon the legitimate supposition that the electro-magnetic excitation of the soft iron operates instantaneously. If this were not the case, my apparatus would have shown that magnetism and electricity ought to be attributed to the motion of material particles, or to oscillations much more perceptible than are those of the propagation of sound. ”

“ It appears to me also remarkable that a wire of copper, platina, or iron can be much more easily amalgamated under the influence of sulphuric acid by mercury containing other metals than by mercury entirely pure. It is desirable that this point should attract the attention of scientific men to make similar experiments with more attention. ”

“ In the note which I had the honour of laying before the Academy of Sciences of Paris I stated that, in accordance with all experiments, magnetism is a power acting like universal gravitation, solely in some function of space. The integral comparable with the known number , represents the mean action furnished by the attraction of two points, and is not at all affected by their relative velocity. The inversion of the poles being effected instantaneously, we should thus have a velocity infinitely accelerated. ”

“ The acid which I employed was extremely weak, and had served for many previous experiments. The development of gas was imperceptible either by sight or smell. Having immersed two thick copper wires in the cups and , and having taken hold of them with my hands dipped in salt water, I received during the motion of the apparatus violent shocks, and felt an extreme pricking sensation in the upper part of my body. The mechanical effect of the apparatus corresponding to the speed of 250 to 300 revolutions in a minute has been valued at half the force of a man. ”

“ In the liquid state the adhesion of the mercury to the metallic body plunged into it and afterwards withdrawn, varies with the rapidity of the motion and with the purity of the mercury. Frequently—I may say always—the inversion takes place too soon or too late, and thus gives rise to an attraction or repulsion, in a contrary direction to the rotation. Moreover it is very difficult to preserve the mercury pure when in contact with other metals; and even the purest mercury is disposed to oxidize easily under the influence of the electric sparks. ”

“ There will be a complete loss of the active force obtained . We know the ill effects of shocks in the movement of machines, but there is here another inconvenience which is not simply mechanical. The soft iron, by these repeated shocks and vibrations, gradually acquires at the surface of contact the nature of steel; there will be a considerable permanent magnetism, and the transient magnetic force, which alone produces the movement, will be weakened in proportion. ”

“ By this the action is considerably weakened, or ceases altogether; for it is very remarkable that copper, silver, or platina, amalgamated on their surface, have scarcely any, or at most an extremely weak power of keeping up an electric current with any other metal. I have often remarked that the first deviation of the needle was very strong, and that at length it returned quickly to its first position of equilibrium, without exhibiting any deviation, whilst the voltaic circuit, composed of zinc and amalgamated copper, remained always closed. ”

“ The direction of the deviation of the needle of the galvanometer determined the place which each alloy ought to occupy. The liquid in which the plates were plunged was sulphuric acid diluted with four parts of water. I must remark, that the slightest change of the surface frequently affects the place of the metals the electrical relation of which does not differ much. It is chiefly in lead and its alloys that this phænomenon is most strikingly exhibited. Lead freshly polished is very positive in relation to lead exposed to the air for some minutes or steeped in any acid. ”

“ In short in order to heat a wire of 1000 inches to the same degree to which a wire of a single inch would be heated by a single pair of plates, it is necessary to disengage 1000 quantities of gas, proceeding from the same number of pairs. ”

“ In short no one can deny that it is the nature of a force not to require time to act, and that, if its different effects were not instantly perceptible, it would then be some molecular motion, under the influence of mechanical laws, which takes place. ”

“ A discussion as to priority is only of historical interest. It is not astonishing that persons, who had scarcely any communication with each other, should have devoted themselves almost at the same time to the study of the same object. ”

“ The discs are arranged upon the axis of rotation, so that the sectors of wood and of metal alternately correspond, as represented by the shaded parts of the figure. are bars of copper, formed as levers, very moveable in their supports: they are intended to conduct the current. The arm of the longest lever forms at its extremity an edge, which rests on the periphery of the corresponding disc. The other arm is bent and plunged into a little jar filled with mercury, . The jars and are united by plates of copper, as represented in figure 1. The action of this commutator will easily be understood. ”

“ I have not yet been able to construct a larger apparatus, and I therefore wished to make as much use as I could of the one I possessed, since it was capable of showing completely the nature of the active forces. ”

“ We leave the appreciation of all these factitious means and of these superadditions to those who are in the habit of constructing machines; they well know their insufficiency, the great loss of working power, and how rapidly all the systems are destroyed, unless the greatest care be paid to the preservation of the active forces. ”

“ For example, the remarkable reaction which prevents the movement from becoming accelerated to infinity has become a new source of power; the exact knowledge of the galvanic action leads to a minimum of the expense attending its maintenance. I have restricted myself in my researches to such experiments as touch immediately upon the object itself ”

“ In general, in order to increase the force of the current to any degree, it is necessary to enlarge the surface of the plates, and at the same time the thickness of the connecting wire or the number of the branches. ”

“ It must be acknowledged that I subsequently found the copper troughs to be ill adapted for electro-magnetic experiments; concentric cylinders, which may be plunged in the liquid, are much better. These cylinders must be fixed firmly enough to remain at the proper distance, without recurring to the interposition of wood or of any other insulating matter. Much more constant galvanic effects may be obtained if the space occupied by the liquid between the two metals be not too narrow; at all events it ought to exceed half an inch. ”

“ As the magnetic attraction decreases rapidly as the distance increases, the integral will always be such a function of the amplitude , that its value will not greatly differ from a constant, being rather considerable. Admitting, for an instant, that the magnetic attraction is in an inverse ratio to the squares of the distances, we shall have , being the distance of the magnetic centres when the bars are placed the nearest possible ”

“ But it will be allowed, that we should have reason to be well satisfied with the mechanical effect of magnetism, if this were the only cause which tended to reduce the accelerated movement to a uniform movement. The limits of such a uniform velocity must be very distant. ”

“ I have read in an extract from the memoir of the Abbé dal Negro inserted in the "Annali delle Sc., 1813 [1833?] , Marzo e Aprile, 105—120," that this author established a remarkable law, viz. that the magnetizing power is in the direct ratio of the perimeter of the electromotor, and that the surface has scarcely any effect in increasing this power. ”