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.

   [Footnote 1:  Zeitschrift des Electrotechnischen Vereines in
   Wien, July, 1883.]

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