24 



[Feb. 21, 



beautiful method was suggested. A few days later, Mr. Jennings an- 

 nounced the results of the evening's work and mentioned that several 

 of the plates that had not been exposed directly, but which were de- 

 veloped along with the others, were found to be fogged. He also men- 

 tioned one, upon Avhich had appeared a mysterious disc, that he was 

 quite unable to account for as the character of the impression was en- 

 tirely different from those that had been obtained in the regular way. 



The matter was forgotten until about ten days ago, when the writer 

 asked Mr. Jennings to look over the records of our early experiments, 

 to see if we ever exposed a plate entirely covered in the plate-holder. 

 He immediately did so, and found the plate upon which had appeared 

 the mysterious disc. A very reasonable explanation now is suggested. 

 The disc is doubtless the shadow picture of one of the coins made while 

 we were viewing the Crookes tubes. To add still more weight to this 

 theory, we repeated, a few days ago, the experiment in the same way 

 that it must have been made, if at all, on that interesting evening. The 

 original plate and the result of the recent experiment, we have the 

 honor of showing you here. Now, gentlemen, we wish it clearly un- 

 derstood that we claim no credit whatever for what seems to have been 

 a most interesting accident, yet the evidence seems quite convincing 

 that the^As^ Routgen shadow picture was really produced almost ex- 

 actly six years ago to-night, in the physical lecture room of the Univer- 

 sity of Pennsylvania. 



Arthur W. Goodspeed. 



University op Pennsylvania, February 31, 1896. 



Prof. Edwin J. Houston's Eemarks were as follows: 



It is unquestionably the fact that although natural truths cry aloud to 

 the scientific inquirer, yet they may long remain unrecognized. We 

 have heard to-night, in the excellent paper Prof. Goodspeed has read, 

 that although the apparatus Ave have just seen was in the possession of 

 the University of Pennsylvania, and although it undoubtedly long ago 

 produced the Rontgen effects, yet they were undetected. I had myself 

 a similar apparatus in the philosophical cabinet of the Central High 

 School ; and the Rontgen rays were unquestionably produced by it, 

 but they were not recognized. Many a case of a curious shadow pho- 

 tograph, appearing mysteriously upon a plate believed to be good, 

 strange shadows coming out, the cause of which could not be detected, 

 wei'e most probably some of these Rontgen photographs. 



The paper we have heard has reviewed in so able a manner the com- 

 paratively few facts that are known concerning this peculiar form of 

 radiant energy, that I may, in my remarks, be forced to repeat some of 

 its statements, but it may, nevertheless, be of interest to you if I do so 

 in other language. 



The term cathode rays is applied to the stream of electrified molecules 



