178 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



into four parts, namely, (1) the electiic generator ; (2) the receiver ; 

 (3) the inductive device, and (4) the line protectors. (1.) The electi'ic 

 genei'ator consists of a local batteiy, a rheotome or automatic vibrator, 

 an induction coil, and a ti"ansmitting key. The wire of the induction 

 coil is short and. of comparatively low resistance. This apparatus is 

 sometimes called " the buzzer." The key is inserted in the local 

 circuit, and when it is closed a strong interrupted primary current 

 charges the induction coil, which in turn charges the condensers and 

 line by induction. (2.) The receiver is the ordinai-y magneto-tele- 

 phone, but is made small and light, and is secured against the ear of 

 the operator. The signals cause a buzz or humming note in the 

 telephone — a short buzz representing a dot, and a prolonged buzz a 

 dash of the Morse alphabet. (3.) The inductive device consists 

 simply of the metallic roofs of the cai-s connected together by metallic 

 conductors on one side, and the railroad telegraph wires on the other, 

 the one forming practically the positive and the other the negative 

 plate of an electrical condenser. When one plate is charged by an 

 electrical current the other becomes charged by induction, just as 

 when a Leyden jar or a condenser is used. The writer was aware of 

 Mr. Edison's suggestion that the intervening air becomes alternately 

 polarized and depolarized by the alternating induced current and that 

 it becomes actually a conductor of said current, but, to his mind, the 

 laws of static iiiduction seemed to sufficiently explain the action of the 

 so-called air telegraph.* (4.) The line protectors have a three-fold 

 object, firstly, to pi-event crossing or grounding of the telegraph wires ; 

 secondly, to provide an unbroken circuit for the induced current 

 during the opening and closing of the keys in the main line; 

 and thirdly, to protect the main line instruments from being in- 

 juriously affected by the strong induced currents of the air telegraph. 

 This is accomplished by the use of condensers. A condenser is in- 

 serted in each branch line and a condenser is used to bridge the 

 Moi'se instruments at each way station. In a condenser two metallic 

 plates, separated bj^ some insulating material such as mica, or waxed- 

 paper, are pressed closely together, one plate forming one pole and 



* Since the reading of this paper before the Canadian Institute Prof. A. E. Dolbear, of Tuflt's 

 College, Mass., claims to have invented a system of electrical communication without wires. 

 From the descriptions of the system that have been made public I infer that it is simply a 

 modification of the Air Telegraph. Condensers are used on the one side in lieu of the metallic 

 roof of the car, and on the other side in lieu of the adjacent telegraph wires. The two con- 

 denisers are only a few rods apart. A. M. R. 



