Section III., ISUii. [ 171 ] Trans. R. S. C. 



XI. — Some Experiments on the JC-Eays. 



By John Cox, M.A., and Hugh L. Callendab, M.A. 

 Professors of Physics, McGill University. Montreal. 

 (Read May 2S, 1896.) 



A few days after the arrival of the news of Rontgen's discovery, on 

 Feb. 7th, the first application of the method to si;rgery in the McDonald 

 Physics Btiilding, was made by the photographic location of a bullet in 

 the leg by Professor Cox. This photograph, together with another of a 

 hand, taken by Messrs. King and Pitcher on the same day, has been 

 described and tigui-ed in the Montreal Medical Journal for March, 1896. 



The tube used for taking this photograph was the phosphorescent 

 lamp tube of Puluj, which has been widely used in German}^ for the same 

 purpose. Out of a collection of upwards of tifty Crookes tubes, obtained 

 from Messrs. G-eissler in 1894, this tube alone was found to retain a sutfi- 

 ciently perfect vacuum for the purpose of X-ray photography. The 

 exposure required in the case of the hand was 45 minutes at a distance 

 of 8 inches. Some of the other tubes were found to give faint results, 

 but they were too weak to be of any practical use. 



Shortly afterwards we received a copy of Xature, of Jan. 23rd, 

 containing an account of some experiments by Swinton, who stated that 

 much better results could be obtained by the tise of the Tesla coil oscil- 

 lating discharge. On trying this method, we found that several of the 

 tubes in which the vacuum was bad, gave much brighter tluorescence than 

 with the Ruhmkortf discharge, but the detinition of the shadows with 

 any of the ordinar}^ tubes was infcripr owing to the double kathode. 

 We also found that the oscillating discharge had a very marked tendency 

 to perforate the tubes. Several of our Greissler tubes were temi)orarily 

 damaged in this way, with the oscillating discharge, whereas we had no 

 such mishap with the direct discharge, although using a ten-inch spark. 



With a view of overcoming these and other difficulties, upwards of 

 30 tubes of difierent patterns were devised and constructed by Professor 

 Callendar, both for the direct and the oscillating discharge. Incidentally 

 a number of anatomical and other photographs, including several surg- 

 ical cases, were taken with these tubes, and most of the experiments of 

 Eontgen and other observers were repeated and verified. These obser- 

 vations were interesting at a time when some phys^icists imagined that 

 the rays proceeded from the anode, or that they could be concentrated 

 and brought to a focus by a glass bell-jar, but the main facts with regard 

 to the X-rays are now so firmly established as to need no further corro- 



