RADIOTELEGRAPHY.? 
[With 1 plate.] 
By ComMENDATORE G. Marconi, LL.D., D.Sc. 
The practical application of electric waves to the purposes of wire- 
less telegraphic transmission over long distances has continued to 
extend to a remarkable degree during the last few years, and many of 
the difficulties, which at the outset appeared almost insurmountable, 
have been gradually overcome, chiefly through the improved knowl- 
edge which we have obtained in regard to the subject generally and 
to the principles involved. 
The experiments which I have been fortunate enough to be able 
to carry out, on a much larger scale than can be done in ordinary 
laboratories, have made possible the investigation of phenomena often 
novel and certainly unexpected. 
Although we have—or believe we have—all the data necessary for 
_ the satisfactory production and reception of electric waves, we are yet 
far from possessing any very exact knowledge concerning the con- 
ditions governing the transmission of these waves through space, 
especially over what may be termed long distances. Although it is 
now perfectly easy to design, construct, and operate stations capable of 
satisfactory commercial working over distances up to 2,500 miles, no 
really clear explanation has yet been given of many absolutely authen- 
ticated facts concerning these waves. Some of these hitherto 
apparent anomalies I shall mention briefly in passing. 
Why is it that when using short waves the distances covered at 
night are usually enormously greater than those traversed in the day 
time, while when using much longer waves the range of transmission 
by day and night is about equal and sometimes even greater by day ? 
What explanation has been given of the fact that the night dis- 
tances obtainable in a north-southerly direction are so much greater 
than those which can be effected in an east-westerly one? 
Why is it that mountains and land generally should greatly obstruct 
the propagation of short waves when sunlight is present and not dur- 
ing the hours of darkness ? 
1 Reprinted by permission from author’s separate of Proceedings of the Royal Institution. Read 
before Royal Institution of Great Britain at weekly evening meeting, Friday, June 2, 1911. 
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