as a string or pipe is to sonorous waves.  In this way the receiver can be made to work only when electric waves of a certain rate are passing through the tube, just as a tuning-fork resounds to a certain note; it being understood that the length of the waves can be regulated by adjusting the balls of the transmitter.  As the etheric waves produced by the sparks, like ripples of water caused by dropping a stone into a pool, travel in all directions from the balls, a single transmitter can work a number of receivers at different stations, provided these are “tuned” by adjusting the conductors V Vl to the length of the waves.

This indeed was the condition of affairs at the time when the young Italian transmitted messages from France to England in March, 1899, and it is a method that since has been found useful over limited distances.  But to the inventor there seemed no reason why wireless telegraphy should be limited by any such distances.  Accordingly he immediately developed his method and his apparatus, having in mind the transmission of signals over considerable intervals.  The first question that arose was the effect of the curvature of the Earth and whether the waves follow the surface of the Earth or were propagated in straight lines, which would require the erection of aerial towers and wires of considerable height.  Then there was the question of the amount of power involved and whether generators or other devices could be used to furnish waves of sufficient intensity to traverse considerable distances.

Little by little progress was made and in January, 1901, wireless communication was established between the Isle of Wight and Lizard in Cornwall, a distance of 186 miles with towers less than 300 feet in height, so that it was demonstrated that the curvature of the Earth did not seriously affect the transmission of the waves, as towers at least a mile high would have been required in case the waves were so cut off.  This was a source of considerable encouragement to Marconi, and his apparatus was further improved so that the resonance of the circuit and the variation of the capacity of the primary circuit of the oscillation transformer made for increased efficiency.  The coherer was still retained and by the end of 1900 enough had been accomplished to warrant Marconi in arranging for trans-Atlantic experiments between Poldhu, Cornwall and the United States, stations being located on Cape Cod and in Newfoundland.  The trans-Atlantic transmission of signals was quite a different matter from working over 100 miles or so in Great Britain.  The single aerial wire was supplanted by a set of fifty almost vertical wires, supported at the top by a horizontal wire stretched between two masts 157 1/2 feet high and 52 1/2 feet apart, converging together at the lower end in the shape of a large fan.  The capacity of the condenser was increased and instead of the battery a small generator was employed so that a spark 1 1/2 inches in length would be discharged