1902.] affecting the Transmission of Electric Waves. 257 



tion, and the jiggers were constructed to receive signals at the maxi- 

 mum distance corresponding to the power and frequency used at the 

 transmitting station. The fundamental wave-length was that adopted in 

 H.M.'s service, except when my syntonic system was used, in which 

 case large variations in the wave-lengths were tried. Syntonic wireless 

 telegraphy, however, is not considered in this paper. 



The results, when tabulated, demonstrate the loss in distance that 

 may be experienced when signalling by means of wireless telegraphy 

 under varying conditions of the atmosphere, and the environment of 

 the ship as regards land compared with the distance obtained under 

 favourable conditions in the open sea. In fact, they show some of 

 the causes which may affect the transmission of waves of electrical 

 induction from an aerial wire over the surface of the globe. The 

 causes are treated in the same order as I observed them in the practical 

 work of wireless telegraphy, and the first case that I consider is the 

 effect of intervening land on the distance at which signals can be 

 recorded. 



This effect, without any recorded exception, is to reduce the maxi- 

 mum distance of signalling from that recorded in the open sea by an 

 amount depending upon the thickness, contour, height, and nature of 

 the land. The curvature of the Earth and its effect on the waves is 

 not taken into account, as at the distances covered in these experiments 

 no effect has been noticed, though carefully watched for when signalling 

 with stations high above the sea-level. 



The effects of intervening land are shown for a few typical and 

 well-authenticated cases, and where no other cause or known source of 

 error existed, in the form of diagrams and tables. In the latter the 

 heights of the mastheads or aerial wires are indicated, also the distance 

 of the intervening land from the ship nearest to it, &c. The particu- 

 lars of the land, the distances at which signals could just be clearly 

 received, and the ratio of the distances at which signals were obtained 

 over water under identical circumstances, and generally on the same 

 day, are also inserted. The diagrams illustrate these details graphi- 

 cally, and show the general contour of the land and its strata. The 

 vertical scale has been greatly exaggerated over the horizontal one, in 

 order to present these data more clearly, and the ratio of the vertical 

 to the horizontal scale is either 25 or 12 J, except in Nos. 4 and 5, 

 where it is 32. 



VOL. LXX. 



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