TELEGRAPHIC SIGNALLING. 49 



for optic telegraphy. In the house of Hofrath Solt- 

 manri. father of an intimate comrade of mine. I had 

 the opportunity of seeing the model of a Wheatstone 

 indicator-telegraph, and had taken part in the attempts 

 to bring it into operation between the dwelling house 

 and the establishment for artificial mineral waters at 

 the end of a large garden. This however never 

 succeeded, and I soon perceived the cause of these 

 failures. It was traceable to the principle on which 

 the apparatus was constructed, which required the 

 turning of a handle with such regularity that the 

 impulses of current produced had always sufficient 

 strength to keep the clock-work of the receiving 

 apparatus in motion. This was not attainable with 

 certainty even if the apparatus worked in the room, 

 and was altogether impossible where an important part 

 of the current was lost through the imperfect insulation 

 of the conductors. 



Leonhardt. trying at the instance of the commission 

 to remedy this defect, caused the impulses to be 

 produced by clock-work, i. e. in quite regular intervals, 

 which was certainly an improvement, but still did 

 not suffice with the varying loss of current. This 

 made it apparent to me that the problem was most 

 completely to be solved by converting the indicator- 

 telegraphs into self-acting machines, each of which 

 would automatically break and make the circuit. If 

 two or more of such electrical machines were connected 

 to a single electrical circuit a fresh impulse could 

 only be given when all the inserted apparatus had 



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