TELEGRAPHING. 177 



28. BuUettino di Bibliografia e di Storia delle Scienze Materaatiche e Fisiche, 



Tomo XVIII. Giugao, 1885. 



29. Bericht liber die Senckenbergische Naturforschende Gesellschaft, Frank- 



furt a. M. 1885. Reiseerionerungen an Algerien und Tunis, von 

 Dr. W. Kobelt, Frankfurt a. M. 



Total 36. 



Mr. William Haldane was elected a member. 



Dr. A. M. Rosebrugh read a paper on "Telegraphing to 

 and from Railway Trains." 



He said the first public test of the new railway telegraph, or the 

 " air telegraph, " as it is now called, took place on the Staten Island 

 railroad on Monday, February 1st., when many messages were sent 

 to and from the train while in motion, with an ease and speed which 

 left nothing to V)e desired. The second public test was made on 

 March 19 between Chicago and Milwaukee on the Chicago, Mil- 

 waukee &. St. Paul railroad, when over 300 messages were inter- 

 changed during the trip to Milwaukee and back, and the test was 

 quite as satisfactory as that on the Staten Island railroad. (The 

 writer here explained the arrangement of the apparatus and the 

 philosophy of the device by two drawings, one representing the ar- 

 rangement on the cars and the other the arrangement at the railway 

 station. ) On the train, one wire is connected with the metallic roof 

 of the cars, while the other is connected with the rails by means of 

 the axle and wheels. At the station, one wire goes to the ground, 

 while the other divides into branches, and is connected with three or 

 more telegraph wires. A condenser is interposed in each of these 

 branch lines, not as a necessaiy part of the air telegraph, but as a 

 protection to the telegraph wires. Both on the train and at the 

 station an induction coil, together with a vibrating reed, is used as the 

 electric generator and a magneto-telephone as a receiver. The signals 

 are given with the ordinary Morse key, which is inserted in the local 

 circuit. When the key on the train is operated, the roofs of the cars 

 become charged with electricity ; this charges the adjacent telegraph 

 wires Vjy static induction, and this in turn charges the receiving 

 telephone at the station through the branch wires and condensers. 

 On the other hand, the generator at the station charges the telegraph 

 wires and the telegraph wires charge the roofs of the cars, which in 

 turn charge the telephone on the train. The several factors that 

 contribute to make the " air telegraph " a possibility are divided 



