WIRELESS TELEGRAPHY. 6j 



order to understand the capabilities of wireless telegraphy we must 

 turn to the scientific study of the electric spark; for its practical 

 employment resides largely in its strength, in its frequency in its 

 position, and in its power to make the air a conductor for elec- 

 tricity. All these points are involved in wireless telegraphy. How, 

 then, shall we study the electric spark? The eye sees only an in- 

 stantaneous flash following a devious path. It can not tell in what 

 direction a spark flies (a flash of lightning, for instance), or indeed 

 whether it has a direction. There is probably no commoner fallacy 

 mankind entertains than the belief that the direction of lightning, 

 or any electric spark, can be ascertained by the eye — that is, the 

 direction from the skv to the earth or from the earth to the skv. 



Ml 



i 



Fig. 7. — Arruugemcut of battuiies of motor i to disturb tlie culicrer) uimX tiie flounder by which 



the messages are received. 



I have repeatedly tested numbers of students in regard to this 

 question, employing sparks four to six feet in length, taking pre- 

 cautions in regard to the concealment of the directions in which 

 I charged the poles of the charging batteries, and I have never 

 found a consensus of opinion in regard to directions. The ordinary 

 photograph, too, reveals no more than the eye can see — a brilliant, 

 devious line or a flaming discharge. 



A large storage battery forms the best means of studying elec- 

 tric sparks, for with it one can run the entire gamut of this phe- 

 nomenon — from the flaming discharge which we see in the arc light 

 on the street to the crackling spark we employ in wireless telegra- 

 phy, and the more powerful discharges of six or more feet in length 

 which closely resemble lightning discharges. A critical study of this 

 gamut throws considerable light on the problem of the possibility 



