Trowbridge and Burhank — Source of the X-rays. 131 



there was a long, narrow tube which ended in a thin bulb. In 

 this bulb was a crystal of calcite which was confined in the 

 bulb by the narrowness of the bore of the connecting tube. 

 This tube showed that X-rays were given off at right angles to 

 the straight wire, for the calcite fluoresced a brilliant red and 

 the fluoroscope showed X-rays proceeding from the inclined 





piece of platinum. This form of tube, moreover, showed that 

 the X-rays are reflected, so to speak, from the interior surface 

 of the glass, for there were multiple shadows of the wire 

 on the sides of the tube which were produced by the X-rays 

 of varying intensity which were developed on the surface of 

 the glass, and which in turn, proceeding from this surface at 



