94 PROCEEDINGS OF THE SOCIETY. 



remained for the future developments to decide, but they would t»e so 



utilized, and it might not be so very long before a 'thing practical 



would be done. 



In reply to questions, Mr. Rheinberg had raised a point as to 

 magnification, and hardly thought that high magnifications would he 

 possible by the method described. lie was probably right, but it was 

 perhaps not yet possible to assign any particular limit. The points 

 mentioned in regard to small diaphragms and such like had engaged his 

 attention, and it seemed to him that given a sufficiently small diaphragm 

 a photograph of an average sized diatom might be obtained provided 

 the photographic plate were sufficiently grainless. 



In regard to Mr. Blood's questions about the X-ray tube : the water- 

 bulb was a cooling arrangement. The cathode stream acting on the 

 anticathode caused the latter to get very hot. In regard to his question 

 about a pinhole camera, he could not definitely answer this, and he con- 

 fessed it was rather a new point. But, given a sufficiently small hole in 

 relation to the size of the source of light, it might be possible to do 

 something in this direction. 



Mr. Cheshire had asked a question about enlargement ; the resulting 

 X-ray photograph was the same size as the object and any enlargement 

 had to be obtained by photographic means. The definition, however, 

 was of a higher order, owing to the fact that the object was in contact 

 with the plate and the X-ray wave-length short. He was in hopes of 

 getting a plate which had no grain whatever, and Mr. Rheinberg had 

 suggested that some organic material such as albumen impregnated with 

 a suitable uranium salt might be used. 



In regard to the possibility of photographing organisms or proto- 

 plasm, that was a question of the opacity of the substance to X-rays. 

 He believed that so far as the ordinary X-ray tube went, one was very 

 much limited. X-rays as usually generated passed through organic sub- 

 stances without much difficulty, but recent investigations showed that 

 X-rays could be produced at much lower potentials than that used on 

 the ordinary X-ray tube. For the latter a pressure of sixty or seventy 

 thousand volts or so might be used, but lately it had been stated that 

 X-rays could be produced at a pressure of only 500 volts. If this were 

 so, the gap between the Schumann waves and the X-rays might be 

 bridged by a series of radiations which varied from the wave-length of ultra- 

 violet light to that of the average X-ray. Perhaps a radiation having 

 an intermediate wave-length might prove to be extremely valuable. It 

 might even happen that among these radiations a particular wave-length 

 and a possible source of energy would be obtained whereby one might 

 be able to arrive at the structure or the differences of character of 

 organic substances which up to the present had not been possible. Dr. 

 Shillington Scales had mentioned his surprise at the nature of the 

 o-ranulations appearing on the skiagraphs having been questioned, and 

 asserted that in his mind there could be no doubt as to their structural 

 origin. If he had done some of these small photographs, he would not 

 have been surprised. In many cases with exceedingly small objects, the 

 structure was smaller than the grain of the plate ; in this case the grain 

 predominated and the structure was not evident. But there were still 



