TELEGRAPHY A.CROSS SPACE. 241 



ously to establish telegraphic communication with the Cape, provided 

 £10,000 were forthcoming to establish the necessary basal circuits in 

 the two countries, and the instruments for creating the currents. My 

 offer was deemed too visionary for acceptance. The thing, however, 

 is quite feasible. The one thing necessary is the adequate base lines 

 or areas. All the rest is detail. 



One must not close this section without reverting to a most pregnant 

 point of advance made about 1888 or 1889 by Dr. Oliver Lodge. When 

 experimenting upon the oscillatory discharge he conceived the happy 

 idea of turning two circuits into resonance; or, as he termed it, " syu- 

 tony " with one another, in such a way that when an oscillating electric 

 spark occurred in one of the circuits the inductive effect on the 

 other immediately set up in it electric oscillations which manifested 

 themselves by an overflow spark. I call this experiment pregnant, 

 because it affords a hint of another possibility, namely, that of sig- 

 naling inductively from one area to another, and using around those 

 areas not merely circuits of wires, but syntonic circuits, which, there- 

 fore, are necessarily much more sensitive in their response one to the 

 other. Some of Tesla's high-frequency experiments also have an 

 obvious bearing on this point. ' 



III. — ELECTRIC WAVE METHODS. 



After Clerk-Maxwell had predicted the existence of electro- magnetic 

 waves, and had shown that their speed of propagation is identical with 

 that of light, it required in reality very little to demonstrate by experi- 

 ment the existence of such waves. But that very little was not actually 

 achieved until the year 1888, when the lamented Prof. Heinrich Hertz 

 showed simple methods of producing, detecting, and measuring these 

 waves. It had been known for many years from the predictions of 

 Kelvin and von Helmholtz, and confirmed by the experiments of Fed- 

 derssen, that in many cases an electric discharge is of an oscillatory 

 character. In the years 1887-88 Lodge, Fitzgerald, and others were 

 investigating the nature of these oscillations and the manner in which 

 they are guided by conducting wires, when Hertz conceived the idea of 

 investigating the disturbances which such oscillatory discharges set 

 up in the surrounding space. He showed that, given a simple appa- 

 ratus, which he called an " oscillator," consisting of two metal plates 

 or conductors, connected by a conductor interrupted at one interme- 

 diate point by a " spark-gap," the oscillator on the appearance of each 

 spark emitted a train of electric waves into the surrounding space. 

 He further showed that if a mere circuit or ring of wire of suitable 

 size, the continuity of which is interrupted at one point by a minute 

 gap, is placed in the path of these traveling waves in a suitable posi- 

 tion, the waves as they reach it set up electric surgings in this wire; 

 and, if sufficiently energetic, cause it to show a small spark in the gap. 

 This simple detecting device he termed a " resonator." Armed with 

 sm 98 16 



