120 ANNUAL OF SCIENTIFIC DISCOVERY. 



length. By this machine, the dot, line, or combination of dots and 

 lines, representing each letter of the alphabet, is produced by an al- 

 most instantaneous action of the electric fluid, proceeding from the 

 touch of an appropriate key, marked with the letter to be represented. 

 There are two row r s of keys, similar to those of a piano-forte, sufficient 

 in number to represent each of the letters of the alphabet, and each of 

 the ten numerals. The keys, marked with the letters which they rep- 

 resent, are arranged in a convenient order for the most rapid use, on a 

 principle similar to that by which types are distributed in a printer's 

 case. The instrument, when in operation, is kept in motion by clock- 

 work. A single touch of a key produces all the dots and lines which 

 represent the appropriate letter. This is done with a speed limited 

 only by the capacity of the recording instrument at the other end of 

 the line to receive the impressions. The dots and marks representing 

 each letter, as formed by the machine, are always of uniform dimen- 

 sions, and separated by spaces of uniform length, and the machine is 

 so simple in its construction as not to be liable to get out of order. 



SIEMENS'S TELEGRAPHIC APPARATUS. 



A REPORT presented to the French Academy states that M. Sie- 

 mens has effected an improvement in the arrangement of alphabetic 

 telegraphs, by means of which the party receiving the message can, at 

 the same time, communicate with the other party without having re- 

 course to a second wire, or in any way disturbing the arrangement of 

 the apparatus or interrupting the delivery of the message. The arma- 

 ture of the electro-magnet is provided with a lever, about an inch long, 

 which produces two very different actions. The effect of the first is, 

 at every double vibration (backwards and forwards), to drive forward 

 the wheel, which is mounted upon the shaft of the needle or indicator, 

 the distance of one tooth, and consequently the needle is carried for- 

 ward a letter. By the second action, it breaks the circuit and stops the 

 current from which it has itself received its motion, but not until it is 

 itself stopped in its forward motion, i. e. when the armature, attracted 

 by the electro-magnet, has approached as near the poles as possible ; 

 the circuit being then broken, the armature ceases to be attracted, and 

 being at once drawn back by its spring, the lever returns to its former 

 position, the circuit is again completed, and the operation is renewed. 

 These isochronal vibrations would continue as long as the battery fur- 

 nished a current of equal intensity. The needle could thus be made to 

 move as fast as the eye can read, but its motion would be a series of 

 jerks, so that nothing could be distinguished. To remedy this, there is 

 a contrivance by which the needle may be stopped for a fraction of a 

 second, so that it will distinctly point out the letter to which attention 

 is to be directed. This is done by having around the dial as many 

 stops as there are signs, and upon each stop its sign is marked. On 

 pressing the finger upon any one of them, a small vertical rod is de- 

 pressed so as to act as a stop to a horizontal lever parallel to the needle 

 and mounted on its axis, w T hich amounts to the same thing as if the 

 needle itself were stopped. In sending a message, the finger is to be 



