ANNIVERSARY ADDRESS. 19 
case) and two primary condensers arranged in Lodge’s manner, the 
“outer coatings” forming the terminals of the primary of a small 
induction coil. The secondary of the coil terminates in another 
condenser, from which the leads pass to the lamp. All the con- 
densers are adjustable. Another point about it is that in order 
to secure a minimum of damping, the primary and secondary cir- 
cuits are turned to respond as closely as possible, as indeed must 
follow from the general principles laid down above. The oscilla- 
tions are produced by the discharge of the primary air condensers 
arranged in the most symmetrical fashion. Ebert considers that 
the loss observed in condensers having dielectric materials other 
than air is due to what is now generally called the “ hysteresis” 
of the dielectric. I do not think that this is necessarily the case, 
but it may pass. The ends of the secondary circuit are connected 
to external electrodes surrounding or partially surrounding an 
exhausted globe in which is placed the phosphorescent substance. 
This substance is then excited by the radiation from the electrodes 
or rather by the kathode rays starting from inside the glass under 
the electrodes and falling on the luminous paint. 
The phosphorescent substance which Ebert uses, he describes as 
the “blue-green luminous paint,” made by a firm of German 
chemists. The most interesting point in connection with the 
matter to the general reader, is the extraordinary efficiency of 
such a lamp, as claimed by Ebert. Everybody who pays for 
his electricity by meter knows that an ordinary 16 C.P. lamp 
uses up energy at a rate of about sixty watts ; or say one-twelfth 
ofa horse power. In other words, if no energy were wasted 
between an engine and the lamp, each horse power developed by 
the engine would keep about twelve lights of 16 C.P. going ; of 
this energy however, vastly little affects our eyes—not more than 
Say five per cent. But all energy affecting the eye does not affect 
the eye equally; it takes, according to Langley, about one 
hundred thousand times as much energy to produce perceptible 
Vision with red light as with yellow-green light. The ordinary 
incandescent lamp however is rather poor in yellow-green rays, 
