HENLEY AND BRETT ? S TELEGRAPH. 



magnetism to these. These electro-magnets act upon a small 

 permanent magnet suspended under the desk, on the axis of the 

 indicating needle, and parallel to it. They deflect this needle on 

 the one side or the other, at the moment they receive the 

 magnetism from the current, and their deflection is continued by 

 the effect of the induced magnetism produced by the permanent 

 magnet on the electro-magnet. 



When the handle is raised, the momentary current being 

 reproduced, but in the contrary direction, the polarity of the 

 electro-magnet at the distant station is reversed, and the needle 

 is deflected in the same manner to the other side. 



BRETT'S pRrsrTixa TELEGRAPH:. 



221. Mr. Brett, who has obtained such well-merited celebrity by 

 his successful exertions in establishing electric communication by- 

 submarine cables between the United Kingdom and the continent 

 of Europe, and more recently between the continents of Europe 

 and Africa, took out, conjointly with Mr. House, a patent for a 

 printing telegraph, the original form of which is represented in 

 fig. 92 (p. 113). 



The apparatus, like that of House's American telegraph, already 

 described, consists of a key-board, which is the transmitting 

 apparatus or commutator, and does not differ in any important 

 particular from that already described. The receiving and 

 pointing apparatus is also very similar, and stands upon the key- 

 board. In front of it is an indicating dial, the hand upon which 

 points successively to the letters printed upon the scroll of paper 

 by the apparatus behind the dial. The printing apparatus, with 

 some modifications, is similar to that of House. 



This telegraph is, or was, lately exhibited at work in the 

 Panopticon of Science, in Leicester Square. 



The Messrs. Brett are understood, however, to be engaged upon 

 the construction of an instrument which is expected to attain the 

 same objects in a more satisfactory manner. 



CELERITY OF TRANSMISSION". 



222. Although it be true that the signals made at any one 

 telegraphic station are rendered instantaneously apparent at 

 another, no matter how distant, it must not therefore be inferred 

 that the transmission of messages by the telegraph is equally 

 instantaneous. Not only is this not the case, but the celerity with 

 which messages are conveyed between station and station, so as to 

 be rendered practically available for the purposes of intercommu- 



