EXPEKIMENTAL ARRANGEMENTS. 



93 



of insulating leather, shown here only in section, their projection 

 being given in Fig. 12 (see letter T). 



The grain of fulminate is always at i. 



The time that elapsed between the two interruptions was 

 estimated by means of the Le Boulenge chronograph, this 

 instrument being capable of measuring to the ^o~o~<T(J f a second. 



Fig. 12. Strip of tin. 



Fig. 13. Coupling section at right angles to the 

 axis of the tube. 



The chronograph (Figs. 15 and 16) consists of two funda- 

 mental parts. 



a. The chronometer T (Fig. 15), a long cylindrical rod sus- 

 pended vertically, provided with zinc casing tubes, E, and held 

 by magnetic attraction to the extremity of an electro-magnet, 

 M, through which passes the first current destined to be 

 broken. 



1. The registering apparatus, T (Fig. 16), a similar cylinder 



