During the various experiments the current traversing the line varied from 7.59 amperes to 7.21 amperes.  No heating of any kind was observed.

M.J.  Bertrand, who communicated a paper to the Academy of Sciences on the subject, commented on the relatively low speeds.  It corresponds to a linear displacement of the surface armatures, in no case exceeding the speed of a locomotive wheel.  The tension reached 5,500 volts., under very satisfactory mechanical conditions, and with a current that in no way endangered the line.  This first experiment is certainly encouraging, and it will be followed by others of a more complete and exhaustive character.  MM.  De Rothschild are now embodying a powerful commission of French and foreign scientists who will follow the subject carefully, and report upon it.  It may be safely predicted that one result of this action will be the development of a new series of observations of the highest technical interest and value.—­Engineering.

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THE LOCKED AND CORDED BOX TRICK.

The trick with the locked and corded box, I believe, is an old one, though perhaps not in its present form.  In late years it has been revived with improvements, and popularized by those clever illusionists, Messrs. Maskelyne & Cook and Dr. Lynn, at the Egyptian Hall.  There are several ways of working the trick or, rather, of arranging the special bit of mechanism wherein the peculiar features of the box consist.  The one I am about to describe is, I think, the best of those I am acquainted with, or at liberty to divulge.  Indeed, I don’t know that any method is better, and this one has the advantage over most others of allowing the performer to get into as well as out of the box, without leaving a trace of his means of ingress.  It will be seen the box is paneled, and all the panels look equally firm and fixed.  As a matter of fact, one of the panels is movable, though the closest scrutiny would fail to discover this if the box and fittings are carefully made and adjusted.  Fig. 1 shows the general appearance of the box, of which the back is the same as the front.  In the box I describe, the end marked + has a movable panel.  The size of the box should be regulated by the size of the performer; but one measuring 3 feet 6 inches long by 2 feet back to front, and 21 inches high, exclusive of the lid, which may be 3 inches, will be of general use.  In making the box it is most important that all sides and panels look alike, and that nothing special in the appearance of the end with the loose panel should attract notice.  Fig. 2 shows this end with fittings drawn half of full size, and it will he seen from this that the framing, A, is 3 inches wide by 11/4 inches thick, and the panel, B, 1/2 inch thick.

[Illustration:  FIG. 1.]

It will be noticed that the top and bottom rails of the frame are rabbeted to receive the panel, but the sides are grooved, the groove in front rail being double the depth of the one in the back rail.