"256 Capt. H. B. Jackson. On some Phenomena [May 1, 



elusion of the 2 minutes, the receiving ship, by means of a short 

 prearranged signal, acknowledged the signals, if received, and stated 

 whether they were clear or broken, or if none had been received. 

 To still further reduce any chance of error, two coherers, or, rather, 

 two complete receivers, were generally used ; they were adjusted to 

 be of equal sensitiveness, or nearly so, and they were used alternately, 

 for about 15 seconds each, or else together, i.e., in parallel. Local 

 excitation of these coherers was also frequently resorted to, as by this 

 means, if the filings have by chance rested in an insensitive position, 

 their excitation and shaking gives the possibility that they may 

 rearrange themselves more sensitively. 



The experiments recorded have, with few exceptions, been carried 

 out under my own personal supervision at one of the stations, and 

 the recording tapes of the receivers were invariably compared with 

 the written notes and log of the transmitting stations, at the earliest 

 opportunity afterwards. 



The distances up to which I have carried out experiments, reach 

 140 nautical miles. In my early experiments, before wireless tele- 

 graphy had developed into its present stage, the distances were com- 

 paratively short, though the results were equally instructive. In the 

 tables of records, in addition to stating the actual distances,- the 

 results are compared to a maximum distance of 100, which represents 

 that obtained at sea under the same circumstances, but without the 

 disturbing causes whose effects were under consideration at the time : 

 so the percentage of loss of distance, under varying circumstances, 

 may be easily compared. 



The trials were all carried out under practical sea-going conditions, 

 and though these may militate against the absolute accuracy obtainable 

 in laboratory experiments, they may eliminate some errors which may 

 affect the observations of Hertzian waves in a closed building, such as 

 the reflection of the waves from the surrounding walls. 



The instruments used were those constructed on what is generally 

 known as the Marconi System, and were either supplied by his com- 

 pany or made to my design for the Admiralty j these types only differ 

 in details. 



As a rule, for transmitting signals, an aerial wire or wires were 

 attached to one of two spark balls fitted to an induction coil, the other 

 ball being earthed ; when, however, my system of syntonic transmis- 

 sion was used, the connection of the aerial was not as above ; this 

 system is indicated by inserting (T) against the results. The induc- 

 tion coils employed have been those capable of giving a 10-inch spark 

 between points in dry air. In all the experiments herein detailed, a 

 jigger, i.e., a small transformer, was used in the aerial wire of the re- 

 ceiving instruments. The aerial wires of all ships and stations were 

 tuned as closely as possible to the same natural frequency of oscilla- 



