48 FIRST LITERARY LABOURS. 



Another question, which had already occupied 

 me for a long time, was that of an exact measurement 

 of the velocity of projectiles. The watchmaker Leon- 

 hardt. known as a skilled mechanician and in the 

 employ of the Artillery Commission, had constructed 

 a clock, which turned an indicator with great velocity, 

 when the latter was electro -magnetically connected 

 with the clock-work. 



The coupling and uncoupling of the indicator by 

 the flying shot was attended however with great 

 difficulties, which in spite of our efforts could not be 

 quite overcome. 



This led me to the idea of the employement of 

 the electric spark for the measurement of velocity. 

 In a paper, published in Poggendorffs Annalen "On 

 the application of the electric spark to the measure- 

 ment of velocity' 7 . I demonstrated the possibility of 

 accurately measuring the velocity of projectiles at 

 every stage of their progress by means of a rapidly 

 rotating polished steel cylinder, on which incident 

 electric sparks could leave a distinct mark. This 

 paper also contained the plan, only many years sub- 

 sequently executed by me. of ascertaining by the 

 same method the velocity of electricity itself in its 

 conductors. 



My interest in electrical experiments was most 

 vividly stimulated by participating in the labours of 

 Leonhardt. who was at the same time occupied with 

 experiments, which the military staff had caused to 

 be instituted, with regard to the substitution of electric 



