PRACTICAL CONSIDERATIONS. In ordinary wire less telegraph practice the first requisite is a powerful wave radiator and the second is a sensi Lon6E-MUIRIIEAD TUN ED The first system of wireless telegraphy based on electric resonance was devised by Sir Oliver Lodge of England, and the oscillator and resonator are illustrated diagrammatieally in Fig. 13. Remit improvements, to be described. have been :folded to the original Lodge system both by 1)r. Lodge and Dr. Alexander Muirhead : the complete apparatus is shown in the accompanying plate.
Ileferring to the diagram, A and 11 represent the sending and receiving circuits respectively; 1, 2, and 1', 2', arc capacity areas made of sheet metal in the form of cones; I and 2 alp connected to the induction coil through the inductances, 5. 5, and the condensers, 4, 4; these are provided for the purpose of increasing the capacity of the oscillator and for prolonging the oscillations in the circuit and to establish a definite fre quency of oscillation and the generation of long electric waves. The capacity areas 1' and 2', B, are similar to those of A; they are connected to the primary of a transformer coil, 6 ; the secondary coil, 7, of the transformer is connected with the coherer, S; the local battery circuits and indicating appliances are not shown in the dia gram, hut are clearly shown on the accompanying plate.
The volleyer of which Fig. 14 is a diagrammatic view is of new type. It consists of a small steel disk a, rotating on a column of mercury, b, contained in the cup (1; con nection is made through the binding screw It and the platinum wire c; a copper brush, k, bearing on the shaft forms connection with the disk, a, thus completing the circuit. 'No relay is employed, but the coherer is connected direct to a siphon re corder.
The capacity areas and instruments are in sulated from the earth by the supports 9, D. A, B. In this system there are no earthed ter minals; the object in eliminating the earth as a factor is that it represents a variable capacity, and by loading it on the oscillator and resonator tuning becomes exceedingly difficult.