Another source of trouble lies in interference by atmospheric electricity. Thunderstorms, especially in the tropics, interfere greatly with the reception of signals, the lightning discharges giving rise to violent, irregular groups of waves which produce loud noises in the telephones. There are also silent electrical disturbances in the atmosphere, and these too produce less strong but equally weird effects. Atmospheric discharges are very irregular, without any real wave-length, so that an operator cannot cut them out by wave-tuning pure and simple in the way just described, as they defy him by affecting equally all adjustments. Fortunately, the irregularity of the atmospherics produces correspondingly irregular sounds in the telephones, quite unlike the clear steady note of a wireless station; and unless the atmospherics are unusually strong this note pierces through them, so that the signals can be read. The effects of lightning discharges are too violent to be got rid of satisfactorily, and practically all that can be done is to reduce the loudness of the noises in the telephones, so that the operator is not temporarily deafened. During violent storms in the near neighbourhood of a station it is usual to connect the aerial directly to earth, so that in the event of its being struck by a flash the electricity passes harmlessly away, instead of injuring the instruments, and possibly also the operators. Marconi stations are always fitted with lightning-arresters. The methods and apparatus we have described so far are those of the Marconi system, and although in practice additional complicated and delicate pieces of apparatus are used, the description given represents the main features of the system. Although Marconi was not the discoverer of the principles of wireless telegraphy, he was the first to produce a practical working system. In 1896 Marconi came from Italy to England, bringing with him his apparatus, and after a number of successful demonstrations of its working, he succeeded in convincing even the most sceptical experts that his system was thoroughly sound. Commencing with a distance of about 100 yards, Marconi rapidly increased the range of his experiments, and by the end of 1897 he succeeded in transmitting signals from Alum Bay, in the Isle of Wight, to a steamer 18 miles away. In 1899 messages were exchanged between British warships 85 miles apart, and the crowning achievement was reached in 1901, when Marconi received readable signals at St. John’s, Newfoundland, from Poldhu in Cornwall, a distance of about 1800 miles. In 1907 the Marconi stations at Clifden and Glace Bay were opened for public service, and by the following year transatlantic wireless communication was in full swing. The sending of wireless signals across the Atlantic was a remarkable accomplishment, but it did not represent by any means the limits of the system, as was shown in 1910. In that