354 THE ADDRESSES, LECTURES, ETC., OF 



Still greater strides are being made at the present time towards 

 a clearer perception of the condition of matter when particles are 

 left some liberty to obey individually the forces brought to bear 

 upon them. By the discharge of high tension electricity through 

 tubes containing highly rarefied gases (Geissler's tubes), phenomena 

 of discharge were produced which were at once most striking and 

 suggestive. The Sprengel pump afforded a means of pushing the 

 exhaustion to limits which had formerly been scarcely reached by 

 the imagination. At each step, the condition of attenuated matter 

 revealed varying properties, when acted upon by electrical dis- 

 charge and magnetic force. The radiometer of Crookes imported 

 a new feature into these inquiries, which at the present time 

 occupy the attention of leading physicists in all countries. 



The means usually employed to produce electrical discharge in 

 vacuum tubes were Ruhmkorff 's coil ; but Mr. Gassiot first suc- 

 ceeded in obtaining the phenomena by means of a galvanic 

 battery of 3,000 Leclanche cells. Mr. De La Rue, in conjunction 

 with his friend Dr. Hugo Miiller, has gone far beyond his pre- 

 decessors in the production of batteries of high potential. At his 

 lecture " On the Phenomena of Electric Discharge," delivered at 

 the Royal Institution in January, 1881, he employed a battery of 

 his own invention consisting of 14,400 cells (14,832 Volts), which 

 gave a current of 0'054 Ampere, and produced a discharge at a 

 distance of 0*71 inch between the terminate. During last year he 

 increased the number of cells to 15,000 (15,450 Yolts), and 

 increased the current to 0*4 Ampere, or eight times that of the 

 battery he used at the Royal Institution. 



"With the enormous potential and perfectly steady current at 

 his disposal, Mr. De La Rue has been able to contribute many 

 interesting facts to the science of electricity. He has shown, for 

 example, that the beautiful phenomena of the stratified discharge 

 in exhausted tubes are but a modification and a magnification of 

 those of the electric arc at ordinary atmospheric pressure. 

 Photography was used in his experiments to record the appearance 

 of the discharge, so as to give a degree of precision otherwise 

 unattainable in the comparison of the phenomena. He has shown 

 that between two points the length of the spark, provided the 

 insulation of the battery is efficacious, is as the square of the 

 number of cells employed. Mr. De La Rue's experiments have 



