1900.] on Wireless Telegraphy. 249 



it was found possible to communicate from the North. Haven, Poole, 

 to Alum Bay, Isle of Wight, with a height of 75 feet, the distance 

 being 18 miles. Later on two installations with vertical wires of 

 double that length, i.e. 150 feet, were erected at a distance of 85 miles 

 apart, and signals were easily obtained between them. According to 

 a rigorous application of the law, 72 miles ought to have been obtained 

 instead of 85 ; but as I have previously stated, the law has been proved 

 only to be approximately correct, the tendency being always on what 

 I might call the right side ; thus we obtain a greater distance than 

 the application of the law would lead us to believe. There is a 

 remarkable circumstance to be noted in the case of the 85 miles sig- 

 nalling. At the Alum Bay station the mast is on the cliff, and there 

 is no curvature of the earth intervening between the two stations ; that 

 is to say, a straight line between the base of the Haven and Alum Bay 

 stations would clear the surface of the sea. But in the case of the 

 85 miles the two stations were located on the sea-level, and between 

 them exists a hill of water, owing to the earth's curvature, amounting 

 to over 1000 feet. If those waves travelled only in straight lines, or 

 the effect was noticeable only across open space, in a direct line, the 

 signals would not have been received, except with a vertical wire 1000 

 feet high at both stations. 



While carrying out some experiments nearly three years ago at 

 Salisbury, Captain Kennedy, R.E., and I tried numerous forms of 

 induction coils wound in the ordinary way, that is, with a great 

 number of turns of wire on the secondary circuit, with the object of 

 increasing, if possible, the distance or range of transmission ; but in 

 every case we observed a very marked decrease in the distance obtain- 

 able with the given amount of energy and height. Similar results 

 were obtained some months later, I am informed, in experiments 

 carried out by the General Post Office engineers at Dover. 



In all our above-mentioned experiments the coils used were those 

 in which the primary consisted of a smaller or larger number of turns 

 of comparative thick wire, and the secondary of several layers of 

 thinner wire. I believe I am right in saying that hundreds of these 

 coils were tried, the result always being that by their employment the 

 possible distance of signalling was considerably diminished instead 

 of being increased. We eventually found an entirely new form of 

 induction coil that would work satisfactorily, and that began to 

 increase the distance of signalling. 



The results given by some of the new form of induction coils have 

 been remarkable. During the naval manoeuvres I had an opportunity 

 of testing how much they increased the range of signalling with a given 

 amount of energy and height. When working between the cruisers 

 Juno and Europa, I ascertained that when the induction coil was 

 omitted from the receiver, the limit distance obtainable was seven miles, 

 but with an improved form of induction coil included, a distance of 

 over sixty miles could be obtained with certainty. This demonstrated 

 that the coils I used at that time increased the possible distance nearly 



Vol. XVI. (No. 94.) s 



