378 



EXPERIMENTAL INVESTIGATIONS. 







,5" 

 ffi 







DESCRIPTION OF PLATE. 



Figs. I to 10 show the spots and rings in the order referred to : it should be 



observed that printed figures give but a very imperfect notion of the 



actual effects. 



Fig. 1 1 is the coil apparatus, the contact-breaker being in front. 

 Fig. 12. The air-pump, of a construction which I proposed many years ago, 



and have found most useful for electrical or chemical experiments on 



gases. 



P. An imperforate piston, with a conical end, which, when pressed 

 down, fits accurately the end of the tube, the apex touching the valve 

 v, which opens outwards. 



A. Aperture for the air to rush from the receiver when the piston has 

 been drawn beyond it. 



B. Bladder containing the gas to be experimented on. 



The piston-rod works air-tight in a collar of leathers, and the opera- 

 tion of the pump will be easily understood without further description. 



If it be required to examine the gas after experiment, a bladder or 

 tube leading to a pneumatic trough can be attached at the extremity 

 over the valve v. 



