Short Continuous Electromagnetic Waves. 97 



the energy-loss due to radiation would have caused a much 

 bigger decrement were a single wire present. In fact, the 

 currents at any time flowing in opposite directions in the 

 two wires annul, at big distances, each other's radiation field, 



Fig". 4. 

 40 



20 



/820 



/824 



/828 



icm.- 



/<932 mm. 



so that both the electric and magnetic fields are limited to the 

 space between the wires and their immediate neighbourhood. 



Fig. 3 finally shows that a wave-length o£ about 3*75 metres 

 can readily be measured within a tenth of a millimetre. It is 

 likely that when the sliding support A of fig. 2 is adjusted 

 with the aid of a micrometer arrangement, still higher 

 accuracy may be obtained. 



There are many measurements to which this apparatus can 

 be applied. Some investigations carried out with it will be 

 described in another paper. 



Cavendish Laboratory, Cambridge. 

 Phil. Mag. S. 6. Vol. 38. No. 223. July 1919. H 



