HERTZIAN \YAVE WIRELESS TELEGRAPHY. 441 



sensitive wave-detecting appliance, to be described more in detail 

 presently, was inserted between the base of the insulated receiving 

 aerial and the earth, but it was subsequently found by him to be a 

 great improvement to act upon the receiving device, not directly by 

 the electromotive force set up in the aerial, but by the induced electro- 

 motive force of a special form of step-up oscillation transformer he 

 calls a 'jigger,' the primary circuit of which was inserted in between 

 the receiving aerial and the earth plate, and the secondary circuit was 

 connected to the sensitive organ of the telegraphic receiving arrange- 

 ments.* A suggestion to employ transformed oscillations in affecting 

 a coherer, had also been described in a patent specification by Sir Oliver 

 Lodge, in 1897, but the essence of success in the use of this device is 

 not merely the employment of a transformer, but of a transformer 

 constructed specially to transform electrical oscillations. 



Turning then to the consideration of the relation existing between 

 the transmitting and receiving aerials, we note that in their simplest 

 form these consist of two similar tall rods of metal placed upright, 

 with their feet in good connection with the earth at two places. We 

 may think of them as two identical lightning conductors, well earthed 

 at the bottom, and supported by non-conducting masts or towers. 

 These rods must be in good connection with the earth, and therefore 

 with it form, as it were, one conductor. If, as usual, these aerials are 

 separated by the sea, the intermediate portion of this circuit is an elec- 

 trolyte. The operations which take place when a signal is sent are as 

 follows : 



At the transmitting station, we set up in the transmitting aerial 

 electric oscillations, of which the frequency may be of the order of a 

 million, i. e., the oscillations as long as they last are at the rate of a 

 million a second. Each spark discharge at the transmitter results, 

 however, only in the jDroduction of a train of a dozen or two oscillations, 

 and these trains succeed each other at a rate depending upon the 

 transmitting arrangements used. Each oscillation in the transmitting 

 aerial is accompanied by the detachment from it of semi-loops of elec- 

 tric strain, as already explained. The alterations of electric strain 

 directed perpendicularly to the earth, and of the associated magnetic 

 force parallel to the earth, constitute an electric wave in the ether, 

 just as the alternations of pressure and motion of air molecules con- 

 stitute an air wave. Associated with these physical actions above 



* Tlie term ' jigger ' is one of those slang terms Avhicli contrive to effect 

 a permanent attachment to various arts and crafts. Similarly, the word 

 ' booster ' is now used for a step-up or voltage-raising transformer or dynamo, 

 inserted in series with an electric supply main. The word ' boost ' is a slang 

 term signifying to raise or lift up. ' To give a real good boost ' is an ex- 

 pression for lending a helping hand. The term ' jigger,' in the same manner, 

 is an adaptation of seaman's term for hoisting tackle or lift. 



