178 ROYAL SOCIETY OF CA^^ADA 



developing the plate, the shadows of the bones, etc.. are found to be 

 double. The distance of any object from the plate, when the [)hotograph 

 was being taken, raa}' be very readily deduced by measuring the distance 

 on the plate between the edges of the two corresponding shadows. 



We applied this method in the attempt to locate a pin which had 

 been accidently swallowed by a schoolboy. As a reference mark, a small 

 ring of No. 20 copper wire was placed over the umbilicus. Two ox})o- 

 ui'es of ten minutes each were given on the same plate, and the tube 

 was shifted an inch and a half between the two, in a horizontal direction. 

 The patient was lying on his back on the plate, which was at a distance 

 of about 20 inches from the focus. The shadows of the pelvis and other 

 bones all show sharp and double edges. The shadows of the fine copper 

 ring, cast through the viscera and spine, at a distance of eight inches 

 from the plate, are so sharp that the diameter of the wire can be 

 measured. The \nn, however, was not found on the plate ; either because 

 it was not there, or because it was kei)t moving by the respiration or the 

 peristaltic action of the intestines. 



Magnetic Experiments. — The only certain point of difference in kind 

 at present recognized as existing between the kathode rays as investigated 

 by Lenai-d and the X-rays of Eontgen, is that the latter are not deflected 

 by a magnet to any appreciable extent. The Eontgen rays far surpass the 

 Lenard yslys in point of penetrative powei-, but the difference here is one 

 of degree only. According to Lenard, kathode rays differing in inten- 

 sity, according to the degree of vacuum, differ also in their penetrative 

 power, and in the extent to which they are deflected by a magnet. It 

 appeared, therefore, quite a tenable hypothesis that the X-rays were 

 really of the same nature precisely as the kathode rays, but that they 

 consisted of that part only of the kathode radiation which was able to 

 survive reflection from the platinum plate and transmission through the 

 glass, and were consequently less liable to subsequent abHor])tion or 

 deflection. 



With our focus tube (owing to the care taken in adjusting the 

 platinum plate, and the consequent minuteness of the focus point, which 

 was less than two milimetres in diameter), we were able to obtain ex- 

 tremely sharp shadows at a considerable distance from the tube and the 

 object casting the shadow. It was therefore easy to verify the statement 

 of' Eontgen to a high degree of accuracy. We also attempted to repro- 

 duce the experiment of Lafay, who states that he obtained a deflection 

 of the X-rays if they were passed through an electrified plate. We did 

 not, however, succeed in obtaining any positive evidence of such an effect. 



It occurred to us that the X-rays might be more amenable to magnetic 

 deflection in a vacuum than in air outside the tube. AVith this idea we 

 tried the eftect of approaching the magnet very clo.se to the tube with 

 the direction of its lines of force tangential to the boundary of the 



