I repeat the question I asked at the beginning of this communication, and hope that it may elicit from you, or some of our scientific men, an explanation of the theory of the action of this form of microphone.

W.C.  BARNEY.

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THE DEMBINSKI MICROPHONIC TELEPHONE TRANSMITTER.

This apparatus, which is shown by Figs. 1, 2, and 3, consists of a wooden case, A, of oblong shape, closed by a lid fixed by hinges to the top or one side of the case.  The lid is actually a frame for holding a piece of wire gauze, L L, through which the sound waves from the voice can pass.  In the case a flat shallow box, E F (or several boxes), is placed, on the lid of which the carbon microphone, D C (Figs. 1 and 3), which is of the ordinary construction, is placed.  The box is of thin wood, coated inside with petroleum lamp black, for the purpose of increasing the resonance.  It is secured in two lateral slides, fixed to the case.  The bottom of the box is pierced with two openings, resembling those in a violin (Fig. 2).  Lengthwise across the bottom are stretched a series of brass spiral springs, G G G, which are tuned to a chromatic scale.  On the bottom of the case a similar series of springs, not shown, are secured.  The apparatus is provided with an induction coil, J, which is connected to the microphone, battery, and telephone receiver (which may be of any known description) in the usual manner.

[Illustration:  Fig. 1.]

The inventors claim that the use of the vibrating springs give to the transmitter an increased power over those at present in use.  They state that the instrument has given very satisfactory results between Ostende and Arlon, a distance of 314 kilometers (about 200 miles).  It does not appear, however, that microphones of the ordinary Gower-Bell type, for example, were tried in competition with the new invention, and in the absence of such tests the mere fact that very satisfactory results were obtained over a length of 200 miles proves very little.  With reference to a statement that whistling could be very clearly heard, we may remark that experience has many times proved that the most indifferent form of transmitter will almost always respond well and even powerfully to such forms of vibration.—­Electrical Review.

[Illustration:  Fig. 2.]

[Illustration:  Fig. 3.]

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NEW GAS LIGHTERS.

We are going to make known to our readers two new styles of electric lighters whose operation is sure and quick, and the use of which is just as economical as that of those quasi-incombustible little pieces of wood that we have been using for some years under the name of matches.

[Illustration:  Fig. 1.—­MODE OF USING THE GAS LIGHTER.]