292 SIGNALLING THROUGH SPACE. 



of one mile and three-quarters. This distance was increased in 

 later experiments, and by transmitting the signal from a height, as 

 from a flying kite, it becomes readable at a distance of eight or 

 nine miles. It remains to be seen how far it can be made to act, 

 but it is evident that the higher the apparatus is placed the more 

 favourable are the conditions, and the distance is proportional to 

 the energy of vibration. 



" A curious feature of this method is that no matter in what 

 direction the receiver is placed with respect to the transmitter the 

 effect is the same. Demonstrations were carried out at the 

 lecture-table, the apparatus actually used for long distances being 

 employed. Messages were sent from one part of the building to 

 another through two or three walls, and the receiver appeared to 

 respond to the signals equally well when shut inside a large sheet- 

 iron box. Messages may be sent from valley to valley even when 

 high hills intervene. As to the secrecy that could be maintained 

 with the use of such a method, the lecturer explained that nothing 

 was left to be desired, for a receiver must be tuned to the fre- 

 quency of the transmitter, and among thousands of different 

 frequencies it would be difficult to find that of an unknown 

 transmitter. The subject was now only in its embryo stage, and 

 had yet a vast field before it. Advantages to be reaped in com- 

 mercial, military, and marine undertakings could hardly as yet be 

 anticipated." 



A Short-Lived Island. — In 1867 a new shoal was discovered 

 in the group of the Tonga or Friendly Islands, In 1877 smoke 

 was seen over the shoal. In 1885 the shoal had become a vol- 

 canic island, more than two miles long and 240 ft. high, and a 

 fierce eruption was taking place within it. In 1886 the island had 

 begun to sink in dimensions, although the next year its highest 

 point was 325 ft. above sea-level. In 1889 its height had dimin- 

 ished one-half and the ocean close around it was more than a 

 mile deep. In 1892 the island rose only about 26 ft. above sea- 

 level. According to the latest information, its complete disappear- 

 ance, under the action of the waves, will not be long delayed. 



