216 Prof. Stokes, On the Nature of the Rontgen Rays. [Nov. 9, 



Everything leads us to regard the X rays as being, like rays 

 of light, some process going on in the ether, and sufficient indica- 

 tions of their polarization appear to have been obtained to lead 

 us, at least when those indications are taken along with the 

 undoubted polarization of the Becquerel rays with which they 

 have so many properties in common, to refer the Rontgen as well 

 as the Becquerel rays to a disturbance transverse to the direction 

 of propagation. The absence of refraction, which is so remarkable 

 a feature of the X rays, leads us to regard their progress through 

 ponderable matter as taking place by vibrations in the ether 

 existing in the interstices between the ponderable molecules ; a 

 view which if correct leads us incidentally to a somewhat novel 

 view as to the mechanism of the refraction of light. The absence, 

 or almost complete absence, of diffraction and interference of the 

 X rays leads to one of two alternatives : — either that they are of 

 excessively short wave length, or that they are non-periodic or 

 only very slightly periodic, the X light being on the latter sup- 

 position regarded as a vast succession of independent pulses 

 analogous to the "hedge-fire" of a regiment of soldiers. According 

 to the author's view, each electrically charged molecule on arrival 

 at the target gives rise to an independent pulse, and the vastness 

 of the number of pulses depends on the vastness of the number 

 of molecules in even a minute portion of ponderable matter. 



(2) On the Contact Relations of certain Systems of Circles 

 and Conies. By Mr W. McF. Orr. 



[This paper will appear in Transactions, Vol. xvi. Part II.] 



(3) On certain cases of Discharge in Vacuo and on the zigzag 

 path of Lightning. By J. Monckman, D.Sc, Downing College. 



Prof. J. J. Thomson, when conducting a series of experiments 

 on the striation of sparks in vacuum tubes, made use of various 

 forms of tubes, among which was one which may be called a 

 multiple arc. It consisted of a rectangular tube with two short 

 ones containing the electrodes (Fig. 1). The two sides CAE 

 and GFD were exactly equal in length. When a discharge took 

 place through the tube, it was observed that at a low pressure the 

 spark passed down one side and on changing the direction of the 

 current, the spark passed down the other side, continuing to change 

 sides on each reversal. 



In order to avoid repetition I will speak of this changing of the 

 spark from one limb to another, when the direction of the current 

 is changed, as the ' Reversal of the Spark.' 



