THE BOOK OF THE LANTEEN. 271 



lamp is portable, convenient, and efficient. But above all 

 devices for signalling I prefer a simple electric arrange- 

 ment. The one that I am in the habit of using consists of 

 a single-stroke electric bell with the gong removed from it. 

 When the current is sent through the coils of the attached 

 magnet, the armature is of course attracted, and a little 

 tap is heard, which, although quite unnoticed by the 

 audience, is easily heard by the operator, who is on the 

 look out for it. I used to employ in connection with the 

 bell, if bell it can be called, a Leclanche battery which 

 was placed just below my reading-desk. While on the 

 desk itself I had an ordinary bell push, connected with 

 both bell and battery. But this arrangement I have since 

 superseded by a better one. The Equitable Telephone 

 Company have brought out an electric bell which is quite 

 independent of battery power, a small magnetic arrange- 

 ment taking its place. This generator, as it is called, is 

 shown at fig. 75. It acts most perfectly, and is destined, 

 I should presume, to work a revolution in electric bell 

 mechanism generally. The only inconvenience in the 

 arrangement is the difficulty that is sometimes found in 

 carrying the wires between the lecturer and the lantern, 

 and so concealing them or putting them out of reach 

 that there is no chance of their being tampered with by 

 mischievous hands. In a lecture theatre, where there is 

 commonly a gallery, the wires can be run round the 

 front of the balcony quite out of sight. In other cases 

 they can be laid on the floor underneath the carpet or 

 matting. In nine cases out of ten there is no difficulty 

 in adjusting them. The signal should be given about 



