XT. APPLICATION*. . 37 J 



neutralise each other in the two sets of coils of the branches of the electro- 

 magnets. 



1678. Apparatus for transmission of two simultaneous 

 Telegrams in the same Telegraphic Wire, from one station to 

 another. 



Elie Wartmann, Professor of Natural Philosophy at the 



University of Geneva. 



A description of the method and apparatus is printed, in the '-' Archives 

 des Sciences physiques et naturelles," Geneva, November 1860. 



1679. Apparatus for permitting any two Stations on the 

 same Telegraphic Wire to communicate immediately without the 

 aid of the intermediate ones, so that the despatch remains secret 

 between them. 



Elie Wartmann, Professor of Natural Philosophy at the 

 University of Geneva. 



For complete description see the " Bibliotheque universelle de Geneve," 

 May 1853. It consists of the following- parts : 



a. Sender ; b. Regulator ; c. Indicator ; d. Interrupter. The principles 

 of the instrument are: 1. To break the communication of every intermediate 

 station with the earth ; 2. To maintain the contact of their electro-magnets 

 with the poles in order to facilitate the transmission of direct currents 

 between the two stations to be united ; 3 To let the officer in the station 

 from which the despatch originates know that it is really received in the 

 proper one ; 4. To cut off immediately the communication after the receipt of 

 an answer ; 5. To reinforce the current of the battery in the first station by 

 means of the batteries in all intermediate stations. 



1238. The First Instrument used to Electrify the Ink- 

 Bottle of the Siphon llecorder. Sir W. Thomson. 



This was the first instrument used for producing the electricity required to 

 electrify the ink-bottle of the siphon recorder. What is now known as the 

 mouse-mill, referred to in Clerk Maxwell's " Electricity and Magnetism," is a 

 modification of this instrument, driven by intermittent electro-magnetic force. 

 Described in Thomson's reprint of " Papers on Electro-statics and Magnet- 

 ism," xxiii, 416-419. 



1239. Modified form of 1238. Sir W. Thomson. 



1240. Further developed form of 1238. 



Sir W. Thomson. 



One of the applications of this is to multiply indefinitely the electro-static 

 indications obtainable from a feebly electrified body on the same principle as 

 Nicholson's Revolving Doubler, and as the rotating induction instrument 

 exhibited by Mr. C. F. Varley at the International Exhibition of 1861. 



1683a. Automatic Lightning Guard. 



Warden, Muir/tead, and Clark ^ 

 1683a. Eggington Automatic Lightning Guard, lor 



protecting submarine cables from the effects of lightning and 

 powerful earth currents. The land wire is automatically put to- 

 earth by the currents themselves and the cable left safely insulated. 



Warden, Muirhead, and Clark. 

 " A a 2 



