186 ROYAL SOCIETY OF CANADA 



baud itself su narrow, that a widening of a quui-ter of a millimetre, 

 corresponding- to an X-ray velocity of 100 kilometres per second, could 

 not fail of being readil}* detected. In fact, the lower limit of the velocity 

 80 far îis may be judged from the evidence of these experiments, is in all 

 probability not less than 200 kilometres per second. 



While these experiments cannot be regarded as proving that the X- 

 rays do not consist of electrified atoms, as some physicists supposed at the 

 time when experiments were undertaken, they at least appear to render 

 * it more improbable than was at first supposed. Such a stream of atoms 

 in air at atmospheric pressure, might be expected to sutFer diffusion or 

 absorption like the kathode or Lenard rays. The velocity found is so 

 manv times greater than ordinary molecular velocities, as to appear 

 improbable even for an electrified atom. It is in the highest degree 

 improbable that such atoms could penetrate solid bodies with the facility 

 shown by the X-rays. The inference is either that the propagation of 

 the X-rays is a process of exchange, if propagated by the aid of material 

 particles, or much more probably that it is some kind of wave motion in 

 the ether, of a frequency too great to suffer regular refraction or reflec- 

 tion. It is interesting to compare the present result with the lower limit 

 of 31-4--4 kilometres per second given by Helmholtz in 1871 for the velo- 

 city of propagation of electrical oscillations. The application of more 

 refined methods to the X-rays, may succeed in showing that this velocity 

 is the same as that of light. 



Phydological Effects of the JC-Rays. — It was natural to try whether 

 the X-rays produced any eff'ect upon the retina or the skin or parts of 

 the body exposed to their action. Positive results have been claimed in 

 many cases though not by atiy observers of mueh repute. As stated by 

 Rontgen, we could not detect that the retina was sensitive to the smallest 

 extent to the most powerful X-radiation which we could produce. This 

 shows that the i)igment of the retina does not flvioresce api^reciably 

 under the influence of the X-rays, as it does under the influence of the 

 ultra violet rays of the spectrum. The X-rays have also been credited 

 with producing blisters and peeling of the skin, and falling out of the 

 hair. AYe have not observed these effects in the most prolonged expo- 

 sures. It is evident, however, that such effects might be produced by the 

 electric sparks from the tube, if it were placed too close to the skin, as is 

 .sometimes done with the object of shortening the exposure. The direct 

 light from the tube also contains a proportion of ultra-violet rays which 

 are known to produce blistering if sufficiently intense. 



It was natural to imagine that the X-rays might possess germicidal 

 ])roperties similar to those of ultra-violet light. That this is not the 

 case, however, has been shown by the agreement of the negative results 

 of many competent observers. With the assistance of Dr. Wyatt 

 Johnston, we submitted cultures of typical bacilli in jelly to the action of 



