OSCILLOGRAPH RECORDER 



109 



clockwork motor ; one or two strings (silver wires 

 Tcfeoth inch thick) are free to move laterally between 

 the tunnelled poles of the electro -magnet,, and a 

 shutter is attached to them where the optic axis 

 meets them. N is a Nernst lamp, and L a lens. 

 The lens in the tube T throws a real image of the 

 shutter over the horizontal slit S. The terminals 

 A, B of the galvanometer strings are connected to 

 the metal drum and stylus of a photo -telegraphic 



M O' 



FIG. 51. 



transmitter, across which capacity can be shunted, 

 or inductance, etc., can be placed in the circuit. 



Every time the stylus of the transmitter comes in 

 contact with the metal, current flows through AB, 

 which is laterally displaced ; hence the shutter 

 uncovers the slit S more or less according to the 

 current strength. A series of images of the slit is 

 thus seen on the moving film MOQ on develop- 

 ment. The elongation and widening of the image 

 due to capacity can be seen clearly on comparing 

 the two records shown in Figs. 52 and 53. 



