SIGNALING THROUGH SPACE WITHOUT WIRES. 257 



by no means reached the limit. It is interesting to read the surmises 

 of others. Half a mile was the wildest dream. ' 



It is easy to transmit many messages in any direction at the same time. 

 It is only necessary to tune the transmitters and receivers to the same 

 frequency or "note." I could show this here, but we are bothered by 

 reflection from the walls. This does not happen in open space. Tuning 

 is very easy. It is siniply necessary to vary the capacity of the 

 receiver, and this is done by increasing the length of the wings W in 

 figure 2. The proper length is found experimentally close to the trans- 

 mitter. It is practically impossible to do so far away. 



It has been said that Mr. Marconi has done nothing new. He has 

 not discovered any new rays; his transmitter is comparatively old; 

 his receiver is based on Branly's coherer. Columbus did not invent 

 the egg, but he showed how to make it stand on its end, and Marconi 

 has produced from known means a new electric eye, more delicate than 

 any known electrical instrument, and a new system of telegraphy that 

 will reach places hitherto inaccessible. There are a great many prac- 

 tical points connected with this system that require to be threshed out 

 in a practical manner before it can be placed on the market, but 

 enough has been done to prove its value, and to show that for shipping 

 and light- house purposes it will be a great and valuable acquisition. 



1 "Unfortunately at present we can not detect the electro-magnetic waves more 

 than 100 feet from their source." — Trowbridge, 1897, What is Electricity, p. 256. 



"I mention 40 yards because that was one of the first out-of-door experiments, 

 but I should think something more like half a mile was nearer the limit of sensi- 

 bility. However, this is a rash statement not at present verified." — Oliver Dodge, 

 1894, The Work of Hertz, p. 18. 

 SM 98 17 



