Page:Federal Reporter, 1st Series, Volume 8.djvu/524

 510 FEDERAL REPORTER. �upon the fifth claim of the first patent, which is much more compre- hensive in ita scope. �Patent No. 174,465, issued to 5ell, dated March 7, 1876, is en- titled "Improvement in Telegraphy," and is said in the specification to consist in — �"The employment of a vibratory or undulatory current of electricity, in con- tradistinction to a merely intermittent or pulsatory current, and of a method of and apparatas for produeing electrical undulations upon the line wire." �The patentee mentions several adVantages whioh may be derived by the use of this undulatory current, instead of the intermittent current, which continually makes and breaks contact, in its applica- tion to multiple telegraphy; that is, sending several messages, or fitrains of music, at once over the same wire, and the possibility of conveying sounds dther than musical notes. This latter application is not the most prominent in the specification; though, as often hap- pens, it has proved to be of surpassing value. This part of the in- vention is shown in figure 7 of the drawings, and is thus desoribed in the text : �"The armature, c, figure 7, is fastened loosely by one extremity to the un- covered leg, d, of the electro-magnet, b, and its other extremity is attached to the center of a stretched membrane, a. A cone, A, ia used to convey sound vibrations upon the membrane. Whari a sound is uttered in the eone, the membrane, a, is set in vibration ; the armature, c, is f orced to partake of the motion; and thus electrical undulations are created upon the circuit E, 6, e,f, g. These undulations aie similar in f orm to the air vibrations caused by the sound; that is, they are represented graphieally by similar curves. The un- dulatory current passing tbrough the electro-magnet, /, influences its arma- ture, Ji, to copy the motions of the armature, c. A similar sound to that uttered in A, is then heard to proceed from L." �With the figure 7 before us, this description is readily understood. A cone of pasteboard, or other suitable material, has a membrane stretched over its smaller end; at a little distance is a piece of iron magnetized by a coil through which is passing a current of electric- ity. When sounds are made at the mouth of cone, A, the membrane vibrates like the drum of a human ear; and the armature, which is direetly front of the' magnet, vibrates with the membrane, and its movements cause pulsations of electricity, like those of the air which excited the membrane, to pass over the wire ; and the wire stretches to another similar magnet and cone with its membrane and armature. The second armature and membrane take up the vibrations and make them audible by repeating them into the condensing cone, L, which translates them into vibrations of the air. ��� �