The tone-receiver consists of an electro-magnet, _m m_, which rests upon a resounding-board, _u w_, and the surrounding coils of which are connected with the metallic circuit and the earth. Opposite to the electro-magnet there stands an armature, which is connected with a lever, _i_, as long as possible but light and broad, and which lever together with the armature, is fastened like a pendulum to the support _k_; its movements are regulated by the screw _l_ and the spring _q_. “In order to increase the effect of the apparatus, this tone-receiver may be placed in the one focus of an elliptically hollowed cavity of sufficient size, while the ear of the person who listens to the reproduced sounds ought to be placed at the second focus of the cavity.” The action of the two apparatus, the general manner of connection of which may be seen from the illustrations--at the one station being the tone-indicator, at the other the tone-receiver--is the following:--By speaking into, singing, or conducting the tones of an instrument into the tube, _a b_, there is produced in the tone-indicator (Fig. 34) in consequence of the condensation and rarefaction of the enclosed column of air, a motion of the membrane, _c_, corresponding to these changes. The lever, _c d_, follows the movements of the membrane, and opens or closes the circuit according as there occurs a condensation or rarefaction of the enclosed air. In consequence of these actions, the electro-magnet, _m m_ (Fig. 13), is correspondingly demagnetised or magnetised, and the armature (and the armature-lever) belonging to it is set into vibrations similar to those of the membrane of the transmitting apparatus. By means of the lever, _i_, connected with the armature, the similar vibrations are transmitted to the surrounding air, and these sounds thus produced finally reach the ear of the listener (the sounding-board increasing the effect). As regards the effectiveness of this apparatus, the author remarks that while the similar number of the produced vibrations is reproduced by the receiver, their original strength has not yet been obtained by it. For this reason also small differences of vibration are difficult to hear, and during the practical experiments hitherto made, chords, melodies, &c., could be, it is true, transmitted with astonishing (?) fidelity, while single words in reading, speaking, &c., were less distinctly perceived. * * * * * [The rest of the article deals with the “square-box” transmitter described in Reis’s Prospectus, and adds nothing to the information already published.]