WIRELESS TRANSMISSION OF ENERGY THOMSON. 257 



of the accuracy of tuning, however, high-power stations may, in fact, 

 cause high frequency waves of high potential in all surrounding wire 

 or metal structures if near enough. Burn outs, or even fires, may 

 occur from this cause. Hence it is desirable that high-power sending 

 stations should be well removed from centers of population where 

 there are electric circuits and electrical apparatus likely to be inter- 

 fered with or injured. 



It may be here pointed out that the limit of potential which is 

 available in wireless transmission is the same as that of long distance 

 transmission by wire and for the same cause. Naturally, if the po- 

 tential on the sending antenna can be raised, the amount of energy 

 which can be put into the wave impulses will be increased, but there 

 comes a time when an increase of potential on the wires of the antenna 

 gives rise to a corona loss — much as the increase of potential in wire 

 transmission produces a corona loss. The conductors of the system, 

 in such a case, are surrounded by a blue discharge which is even 

 visible at night and which frequently can be heard. When this con- 

 dition is reached every further increase of potential simply increases 

 the corona loss without adding correspondingly to the energy trans- 

 mission. Just as in wire transmission it can be aA^oided by increas- 

 ing the diameter of the conductors, so in wireless work it could be 

 avoided by constructing the antenna system of hollow tubes with 

 smooth exteriors, and the imagination may be permitted to depict a 

 sending tower of polished metal surmounted by a sphere of similar 

 material and worked at millions of volts. No limit can be set to the 

 amount of energy which might thus be radiated, and no limit as yet 

 can be set to the distance around the earth to which signals might 

 be sent by such means. 



One curious fact which has been developed in the Avork of wireless 

 signaling is that da^dight, especially sunlight, is very detrimental to 

 transmission as compared with the night. That is to say, if the wire- 

 less waves are to traverse the sea surface in sunshine, the chance of 

 receiving them in suiRcient force to produce signals at great distances 

 is far less than when they are sent at night. It is probable that this 

 difference is not due to any single cause — it may be the effect of a 

 combination of causes. It is a notable fact, too, that this difference 

 between the effectiveness of daylight transmission and night trans- 

 mission is accentuated at the higher frequencies. 



Though the cause is still somewhat obscure, we may venture a 

 suggestion or hypothesis which may have a bearing on the case. 

 Referring to figure 23, we have tried to show the condition. The 

 electrostatic field at the water surfa,ce at the same instant is as in 

 figure 21 produced in zones around the antenna A, spreading with 

 tipproximately the speed of light. It is well known that under the 

 44863°— SM 1913 17 



