( 321 ) 



of both spaces i=0, j =0 for cusps ; in each of these points the 

 section of the phine with the osculating space of j = form the 

 cuspidal tangent. As is known the space i> =r 0, also by the aid of 

 its double surface i = Q , j = 0, divides the space 6* into three parts 

 containing the points for which the number of the real osculating 

 spaces passing through them is successively 4, 2 and 0. 



Physics. — Prof. Haga made, both on behalf of himself and Dr. 

 C. H. Wind a communication: „On the deflexion of X-rays". 



Deflexion of X-rays was proved on the experiment being arranged 

 as follows : 



The RöKTGEN-tube was placed behind a slit 1 cm. high and 

 14: microns wide; at 75 cm. from the latter was the diffraction slit, 

 which gradually diminished in width from 14 to about 2 microns. 

 The photographic plate was placed at 75 cm. from the diffraction 

 slit. Time of exposure from 100 to 200 hours. The image of the 

 slit first became narrower and then showed an unmistakable broa- 

 dening. From the width of the part of the diffraction slit corres- 

 ponding to this broadening and the character of the broadening au 

 estimination can be made of the wavelength. It appeared that X-rays 

 exist of about O.l to 2V3 Angstrom units, comprissing 4 octaves. 



(A detailed paper will appear in the Proceedings of the next meeting). 



Physiology. — Prof. Stokvis presented for the Library the 

 inaugural dissertation of Dr. G. Bellaar Spruyt: „On the 

 physiuhgical action of metlujlnitramine in connection with its 

 chemical constitution." 



At different occasions our member Prof. Franchimont exposed 

 in our meetings his views about the chemical structure of nitra- 

 mines, especially of methylnitramine. Till yet the question about 

 the intimate chemical constitution of these compounds, in reference 

 to the manner, in which their nitrogen is linked with the other 

 elements, is an open one. Whereas some authors believe, that the 

 nitrogen of nitramines is linked with hydroxyle, so that the whole 

 compound is a species of nitrite: H — — N = 0, Prof. Fran- 

 CHiMONT rejects this view, and considers it linked in a cyclical 



/O ^0 



way, for instance H — X | or H — X . As Prot. Franchi- 



MONT considered it of some value to study the physiological action 

 of nitramines, to the aim of throwing more light on the open 



22 



froceediugs Royal Acad. Amstcalam. Vol. I. 



