Chap. XVI.] 



THE CHRONOGRAPH. 



Fig. 85. Marey's 

 Vibrating Style. 



a steel spring which runs between the bobbins. The 



current is brought to the binding screws d d. When 



the keepers are magnetic both act 



on the little wedge, and pull it 



down into the space between them. 



When they are in proper position 



they should act equally so as not to 



attract the wedge to one side or 



other. When the keepers are de- 

 magnetised the wedge is pulled 



upwards by the spring. A finely 



pointed piece of quill projects from 



the wedge as marker. The current 



circulating round the bobbins is interrupted by a 



tuning fork, as shown in Fig. 86. 



The tuning fork is fixed horizontally to a wooden 



support, and has between its limbs, or at the side, a 



small electro-magnet, marked Elect, in the figure. On 



the support are two binding screws, one connected 



with the magnet, 

 the other with the 

 fork. The fork 

 carries at the end 

 of one limb a small 

 piece of fine plati- 

 num wire, which 

 can be made to 

 touch a small plate 



Fig. 86. Tuning Fork for Chronograph. of platinum Sup- 

 ported, by means 



of a screw, on a brass upright Pt. This upright is 

 connected with one end of the wire round the electro- 

 magnet. The current from the element E enters by 

 the binding screw connected with the fork along w T hich 

 it passes to the limb bearing the wire. From the 

 wire it escapes to the platinum plate on the upright, 

 and from this passes round the bobbins, magnetising 



