130 Trowbridge and Burbank — Source of the X-rays. 



Before the straight tube was exhausted powerful brush dis- 

 charges were given off at the ends of the tube. When the 

 tube was exhausted these brushes were much diminished and 

 were replaced by a powerful brush which came off from the 

 straight wire through the bulb of the tube and speedily punc- 

 tured the latter when any object, even an insulator, was 

 brought within six inches of the bulb. The most interesting 

 results obtained with this form of tube was the production of 

 the so-called X-ray burn by means of the brush discharge 

 from its bulb. When the back of the hand was exposed to 

 this brush discharge, which assumed a peculiar forked nature 

 in the dark-room, a peculiar prickling sensation was expe- 

 rienced and all the symptoms of the well-known X-ray burn 

 developed. The skin when examined under a microscope 

 exhibited an appearance similar to that shown by the photo- 

 graphic plate. There were centers of inflammation surrounded 

 by regions of lesser degrees of burn. It seems evident that 

 the so-called X-ray burn is due to an electrification — a dis- 

 charge at the surface of the skin — and this electrification may 

 or may not be accompanied by the X-rays. This first form of 

 tube was then abandoned, and a straight wire tube alone (fig. 

 2) was employed. Similar results were obtained with this 

 tube. It was significant that the whole interior of this tube 

 fluoresced brilliantly when it formed part of a circuit through 

 which a disruptive discharge passed. This latter form of tube 

 was replaced by that represented in fig. 3. A side ending 

 in a thin bulb was added to the straight wire tube. The same 

 phenomenon was exhibited by this tube : in addition a brilliant 

 fluorescence filled the side tube, which appeared to flow in or 

 flow out of the narrow tube which ended in the small bulb. 

 We were reminded by this phenomena of Poynting's hypothesis 

 of the flow of energy into a wire. This form of tube was replaced 

 by a straight wire tube which is represented in fig. 4 and fig. 5 

 (side view). A straight wire passed completely through the tube 

 and was in circuit with a line on which there was a rapid change 

 of potential. At one end of this tube opposite a thin bulb 

 blown on the tube is a piece of platinum foil inclined like the 

 ordinary focus plane in a focus tube. At first we connected 

 this focus plane with the ground, and having ascertained 

 that X-rays were given off very strongly from this foil, we 

 removed the ground connection and substituted for it a sheet 

 of zinc. The tube still gave off X-rays. We then removed 

 the sheet of zinc and found that X-rays were given off with 

 undiminished strength. This tube was then modified into the 

 form represented in fig. 6 and fig. 7 (side view). The straight 

 wire occupied the middle of a tube : in one end of this tube 

 was placed a focus plane of platinum and at the other end 



