Rowland, Carmichael and Briggs — Rontgen Rays. 247 



Art. XXYIII. — Notes of Observations on the Rontgen rays ; 

 by Henry A. Rowland, IS". R. Carmichael and L. J. 

 Briggs. 



The discovery of Hertz some years since that the cathode 

 rays penetrated some opaque bodies like aluminium, has opened 

 up a wonderful field of research, which has now culminated in 

 the discovery by Rontgen of still other rays having even more 

 remarkable properties. We have confirmed, in many respects, 

 the researches of the latter on these rays and have repeated 

 his experiment in photographing through wood, aluminium, 

 cardboard, hard rubber and even the larger part of a millimeter 

 of sheet copper. 



Some of these photographs have been indistinct, indicating 

 a source of these rays of considerable extent, while others have 

 been so sharp and clear cut that the shadow of a coin at the 

 distance of 2 cm from the photographic plate has no penumbra 

 whatever, but appears perfectly sharp even with a low power 

 microscope. 



So far as yet observed the rays proceed in straight lines and 

 all efforts to deflect them by a strong magnet either within or 

 without the tube have failed. Likewise prisms of wood and vul- 

 canite have no action whatever so far as seen and, contrary to 

 Rontgen, no trace of reflection from a steel mirror at a large 

 angle of incidence could be observed. In this latter experi- 

 ment the mirror was on the side of the photographic plate 

 next to the source of the rays and not behind it as in Rontgen' s 

 method. 



We have, in the short time we have been at work, princi- 

 pally devoted ourselves to finding the source of the rays. For 

 this purpose one of our tubes made for showing that electricity 

 will not pass through a vacuum, was found to give remarkable 

 results. This tube had the aluminium poles within l mm of 

 each other and had such a perfect vacuum that sparks gener- 

 ally preferred 10 cm in air to passage through the tube. By 

 using potential enough, however, the discharge from an ordi- 

 nary Ruhmkorff coil could be forced through. The resistance 

 being so high the discharge was not oscillatory as in ordinary 

 tubes but only went in one direction. 



In this tube we demonstrated conclusively that the main 

 source of the rays was a minute point on the anode nearest to 

 the cathode. At times a minute point of light appeared at 

 this point but not always. 



Added to this source the whole of the anode gave out a few 

 rays. From the cathode no rays whatever came, neither were 



