6 THE SCIENTIFIC PAPERS OP 



The instruments he used (which were exhibited on the table) 

 were both of the pointing and the printing classes. The 

 former consisted in the outward arrangement of the dial, around 

 which were placed thirty radial keys, each of which bore a letter of 

 the alphabet, or other sign (the letters which most frequently 

 occurred being repeated at opposite points). A hand on the dial 

 revolved continually when the circuit with the battery was com- 

 pleted, but was stopped opposite any key which was depressed by 

 the operator. A similar instrument was placed at every station, 

 the hands of which were compelled to rotate and to stop in concert, 

 by depression of a key at either station. 



When the telegraph was not used, the batteries of all the stations 

 were disconnected from the instruments. 



The first step then in sending a message was to move a small 

 handle (whereby the battery of the station was put into circuit), 

 the effect of which was to ring a bell at the nearest station. On 

 hearing the alarm, the officer at that station also moved the 

 handle of the instrument before him, and the dial hands of both 

 rotated simultaneously. The message was thereupon transmitted by 

 simply spelling the words by the depression of the keys on the one 

 side, and by reading the letters indicated by momentary stoppages 

 of the pointer on the other. If the officer at the second station 

 received only a sign denoting a succeeding station, he had to move 

 the handle into a third position, whereby he excluded the instru- 

 ment at his station, and gave the alarm at the following, and so 

 on. When in another position all the instruments along the line 

 were in circuit, and received the message simultaneously. 



The instrument was well adapted for railway service, and for 

 intermediate correspondence generally, because it could be worked 

 at first sight by any uninitiated person. It afforded peculiar 

 facilities for communicating either to one or many stations 

 collectively, and it permitted the ringing of bells, and other signals 

 through one and the same wire, without causing confusion in the 

 transmission of messages. 



He might mention as an instance the line from Berlin to 

 Hamburg, where one main wire served for the transmission of 

 messages, and for announcing the progress of every train from 

 station to station, by the ringing of large bells, which were 

 stationed at every crossing, and at such distances apart that the one 



