104 POPULAR SCIENCE MONTHLY. 



them as a material radiation, and which, as it appears to me, 

 might be thus enunciated. In the neighborhood of the cathode, 

 the electric field is sufficiently intense to break into pieces (into 

 ions) certain of the molecules of the residual gas. The negative 

 ions move toward the region where the potential is increasing, 

 acquire a considerable speed, and form the cathode rays ; their 

 electric charge, and consequently their mass (at the rate of one 

 valence-gramme for a hundred thousand coulombs), is easily meas- 

 urable. The positive ions move in the opposite direction ; they 

 form a diffused brush, sensitive to the magnet, and not a radiation 

 in the correct sense of the word." 



Nikola Tesla, in a recent Electrical Review, describes the fol- 

 lowing experiment, which seems to support the view that these 

 rays are material radiations : When an exhausted bulb is attached 

 to the terminal of a disruptive coil, small streamers are observed 

 which often break through the side of the bulb, producing a fine 

 hole. " Now, the extraordinary thing is that, in spite of the con- 

 nection to the outer atmosphere, the air can not rush into the 

 bulb as long as the hole is very small. The glass at the place 

 where the rupture is may grow very hot to such a degree as to 

 soften; but it will not collapse, but rather bulge out, showing 

 that a pressure from the inside greater than that of the atmos- 

 phere exists. On frequent occasions the hole becomes so large 

 as to be perfectly distinguishable to the eye. As the matter is 

 expelled from the bulb the rarefaction increases and the streamer 

 becomes less and less intense, whereupon the glass closes again, 

 hermetically sealing the opening." He reports producing strong 

 pictures at a distance of forty feet by the use of a bulb with a 

 single terminal, which permits the use of practically any desired 

 potential. 



An account of some important experiments by L. Benoist and 

 D. Hurmuzeson appears in the Comptes Rendus. They caused 

 the rays of a Crookes tube, incited by a powerful coil, to act upon 

 the gold leaves of a Hurmuzeson electroscope at the distance of 

 about twenty centimetres from the tube, and alternately charged 

 with positive and negative electricity. The insulation obtained 

 by a disk of dielectrine which closes the tube admits of the per- 

 fect preservation of its charge for several months. The X rays 

 immediately and completely discharge the electroscope, more 

 rapidly if the charge is negative than if it is positive. " We have 

 thus," they say, "a new way of investigation applicable to the 

 study of these rays, and enabling us to gain important informa- 

 tion as to their real nature. The plate to be studied being put 

 in its place, the electroscope charged to about a divergence of 

 forty degrees, the keeping tube replaced, and the Crookes tube 

 set in activity, we have observed : 



