268 Capt. EL B. Jackson. On some Phenomena [May 1, 



concluded shortly after, owing to intervening land. A few hours later 

 a heavy winter gale came on, and its approach had evidently been fore- 

 told by the falling barometer, the loss of distance in signalling, and 

 the electrical disturbances in the atmosphere, as shown by the signals 

 received on the instruments. No lightning flashes were observed. 



On another occasion, during a period of strong but intermittent 

 .atmospheric effects, no signals were obtainable between two ships up 

 to the usual maximum signal distance. When separated 50 per cent, 

 beyond this distance, and immediately after a particularly strong and 

 persistent series of electrical discharges, the latter half of a signal which 

 was being transmitted very slowly, was correctly deciphered at a 

 distance then considered phenomenal, with the instruments employed 

 at the time. A few minutes later, the atmospheric effects vanished, 

 and with them all signs of further signals, till the ships had closed to 

 their usual signalling distance. This demonstrates that the actual 

 electrical discharges do not of themselves reduce the signalling dis- 

 tance or transmission of the waves at all times, but that they may, 

 under some circumstances, assist that transmission, possibly by a 

 •cumulative effect of the waves emitted by the discharges on the 

 waves emitted by the transmitter, these combining and increasing the 

 effect in the receiver. I have recorded several similar results, which I 

 cannot attribute to any other cause. 



Another effect which reduces the usual signalling distance, is one 

 that I attribute to the presence of material particles held in suspension 

 by the water spherules in a moist atmosphere. 



The Mediterranean Sea is, for days together, frequently exposed to 

 the force of the scirocco wind ; this south-easterly wind is laden with 

 damp, and often charged with salt from spray, and dust particles from 

 the African coast. During the continuance of these winds, the 

 maximum signal distance is generally less than in winds (wet or dry) 

 from any other quarter, the proportional distance being from about 

 60 to 80 per cent. The effect of a scirocco wind can be and is allowed 

 for in practical wireless telegraphy. 



The causes that I have considered above, and which all tend to 

 lessen the maximum signalling distance that would obtain under 

 more favourable circumstances, may all be attributed to influences 

 which are beyond the control of the designers or operators of the 

 instruments used in wireless telegraphy. 



I have now, however, to consider a phenomenon which I can only 

 assign to the apparatus in which the waves of electrical induction are 

 generated. This phenomenon manifests itself by the gradual weaken- 

 ing and occasionally by the total cessation of signals, as the distance 

 between the two ships increases, up to a certain point, and their 

 reappearance as the distance is still further increased ; in the majority 

 of cases, the weakening of signals occurs at, or about, half the signalling 



