Bending of Electric Waves round the Earth. 435 



This is, I think, due to the screen becoming positively elec- 

 trified as soon as it enters the first layer, where, as we know, 

 there is a great accumulation of positive electricity. The 

 positively electrified screen repels the positively electrified 

 Ganalstrahlen which pass it on their way to the cathode, and 

 deflects them from their course so that they now strike the 

 cathode outside the projection of the screen on the cathode ; 

 in this way a considerably larger area of the cathode is 

 screened from the Canalstrahlen, the portion so screened no 

 longer emits cathode rays, and the region in front of it is 

 traversed by little if any current, and the bombardment by 

 retrograde rays almost ceases. 



The same effect can also easily be shown if the mica screen 

 be replaced by a very fine platinum wire. AVhenthis wire is 

 moved across into the dark space it becomes red hot, and 

 sremains so until it enters the first layer. It then immedi- 

 ately becomes cool, and the shadow which before could 

 hardly be detected now becomes prominent and much thicker 

 than the wire ; the change takes place very abruptly. In 

 some cases, before the wire entered this layer I have observed 

 a reversal of the shadow, i. <?., the projection of the wire on 

 the cathode instead of being darker was brighter than the 

 rest of the cathode. This, I think, indicates that the wire in 

 this position got negatively electrified and attracted the 

 ( analstrahlen, instead of repelling them. 



The retrograde rays are formed quite well with gauze 

 electrodes, indicating, I think, that some of them start from 

 the positively electrified first layer, and not from the metal of 

 the cathode. 



XLIII. On the Bending of Electric Waves round the Earth. II. 

 By J. W. Nicholson', Af. A.. D.Sc* 



TN a former notef two criticisms were directed against 

 an investigation, by M. Poincare, of the extent to which 

 diffraction can account for the remarkable results achieved 

 by experimenters in wireless telegraphy. It was indicated 

 that the results of M. Poincare were at variance with those 

 of a paper by the writer, completed some time ago, but only 

 now in course of printing. The difference was traced to two 

 points in M. Poincare's investigation which were mathema- 

 tically unsound. In the meantime M. Poincare has also 



* Communicated by the Author, 

 t Phil. Mag. Feb. 1910. 



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