At the origin of every science, of whatever nature it may be, there is always a fruitless period, of greater or less length, characterized by the warfare of a few superior minds against general apathy. The finest discoveries pass unperceived, so to speak, since they cannot cross the limits of a narrow circle; and it often happens that they fall into oblivion before they have been seriously judged. Meanwhile, a slow progress is imperceptibly made, and, in measure as theoretical principles more clearly disengage themselves, a few industrial applications spring up and have the effect of awakening curiosity. An impulse is thus given, and from this moment a movement in advance goes on increasing at a headlong pace from day to day.

With electricity this period has been of comparatively short duration, since scarcely a century and a half separate us from the first experiments made in this line of research. Now that it has truly taken its place in a rank with the other sciences, we like to go back to the hesitations of the first hour, and trace, step by step, the history of the progress made, so as to assign to each one that portion of the merit that belongs to him in the common work. When we thus cast a retrospective glance we find ourselves in the presence of one strange fact, and that is the simultaneousness of discoveries. That an absolutely original idea, fertile in practical consequences, should rise at a given moment in a fine brain is well; we admire the discovery, and, in spite of us, a little surprise mingles with our admiration. But is it not a truly curious thing that several individuals should have had at nearly the same time that idea that was so astonishing in one? This, however, is a fact that the history of electrical inventions offers more than one example of. No one ignores the fact that the invention of the telephone gave rise to a notorious lawsuit, two inventors having had this ingenious apparatus patented on the same day and at nearly the same hour. This is one example among a thousand.

In the history of dynamo-electric machines it is an equally delicate matter to fix upon the one to whom belongs the honor of having first clearly conceived the possibility of engendering continuous currents.

We do not wish to take up this debate nor to go over the history of the question again. Every one knows that the first continuous current electric generator whose form was practical is due to Zenobius Gramme, and dates back to July, 1871, an epoch at which appeared a memoir (entitled "Note upon a magneto-electric machine that produces continuous currents") that was read to the Academy of Sciences by Mr. Jamin. Ten years previous, Pacinotti had had a glimpse of the phenomenon, and of its practical realization, but was unfortunately unable to appreciate the importance of his discovery and the benefit that might be reaped from it. It is of slight consequence whether Gramme knew of this experiment or not, for the glory that attaches to his name could not be diminished for all that. But an interesting fact that we propose to dwell upon now has recently been brought to light in an electrical review published at Vienna.1 It results from documents whose authenticity cannot be doubted that, as far back as 1867, Mr. L. Pfaundler, a professor at Innsbruck, very clearly announced the reversibility of a magneto-electric motor constructed by Kravogl, a mechanician of the same place, and that he succeeded some time before Gramme in obtaining continuous currents.

The Kravogl motor that figured at the Universal Exhibition of 1867 is but little known, and it is now very difficult to obtain drawings of it. What is certain is that this motor is an application of the properties of the solenoid, and, from this standpoint, resembles the Bessolo motor that was patented in 1855. We may figure the apparatus to our mind very well if we suppose that in the Gramme ring a half and almost two-thirds of the core are removed, and the spirals are movable around the said core. If a current be sent into a portion of the spirals only, and in such a way that only half of the core be exposed, the latter will move with respect to the bobbin or the bobbin with respect to the core, according as we suppose the solenoid or the bobbin fixed. In the first case we have a Bessolo motor, and in the second a Kravogl one.

In order to obtain a continuous motion it is only necessary to allow the current to circulate successively in the different portions of the solenoid. It is difficult to keep the core in place, since it is unreachable, being placed in the interior of the bobbin. Kravogl solved this difficulty by constructing a hollow core into which he poured melted lead. This heavy piece, mounted upon rollers, assumed a position of equilibrium that resulted from its weight, from friction, and from magnetic attraction. But for a current of given intensity this position, once reached, did not vary, and so necessitated a simple adjustment of the rubbers. Under such circumstances, with a somewhat large number of sections, the polarity of the core was nearly constant. The spirals as a whole were attached to a soft iron armature that had the effect of closing up the lines of forces and forming a shell, so to speak.

Like Bessolo, Kravogl never thought of making anything but a motor, and did not perceive that his machine was reversible. It results from some correspondence between Dr. A. Von Waltenhofen and Mr. L. Pfaundler at this epoch that the latter clearly saw the possibility of utilizing this motor as a current generator. Under date of November 9, 1867, he wrote, in speaking of the Kravogl motor, which had just been taken to Innsbruck in order to send it to Paris. "I regret that I shall not be able to see it any more, for I should have liked to try to make it act in an opposite direction, that is to say, to produce a current or an electric light by means of mechanical work." A little more than two years later these experiments were carried out on a larger motor constructed by Kravogl in 1869, and Mr. Pfaundler was enabled to write as follows: "Upon running the machine by hand we obtain a current whose energy is that of one Bunsen element." This letter is dated February 11, 1870, that is to say, it is a year anterior to the note of Gramme.