( 264 ) 
for 63 is not divisible by 12. In the second example of the 
twelve points in Sj) this is likewise proved for the configuration 
of the 13305600 lines from the fact, that 18 is not a factor of 120. 
However, the numbers of constants of plane and four-dimensional 
space in Sjo, namely 24 and 30, being factors of 120, considerations 
of another kind only can teach us that the 15400 planes and 
10395 spaces S, cannot be determined by some of them crossing 
each other. So a characteristic difference between these two examples 
in So and the configuration of Spare would already appear if it was 
proved that five planes in a narrower sense do not lead to 55 planes 
through the 220 points, and four spaces S, in a narrower sense 
not to eleven spaces S, through the 66 points. And should this 
prove to be the case in one of the two, there still remains the 
difference that in S, five lines are found intersecting six arbitrary 
planes and that these lines are related in such a way that each 
line cutting four of the five lines also cuts the fifth ; whilst according 
to a general formula of Scuupert (Mitt. der math. Gesellschaft in 
Hamburg, vol. 2, pag. 87, 1883) in So are found not only 55 but 
116848170 planes and not only 11 but 689289872070 spaces Sy, 
which have respectively a point in common with each of the 24 
arbitrary spaces S, and with each of the 30 arbitrary spaces §;. 
Finally we must stated that H. W. Ricumonp has made the figure 
of the six arbitrary points in the space S,, called by him “hexastigm”’, 
the subject of two papers (Quarterly Journal of Math., vol. 31,’ 
pag. 125—160, 1899 and Math. Ann., vol. 53, pag. 161—176, 1900). 
In these important studies the configuration of SEGRE and its simplest 
analytical representation is brought into close connection with 
G. VERONESE’s theorems about the Pascan hexagram; but, com- 
paratively spoken, the curved space of SeGRE is only cursorily 
mentioned. 
Chemistry. — Professor Lopry DE BRUYN presents a communi- 
cation from Dr. J.J. BLANKSMA: “On the influence of different 
atoms and atomic groups en the conversion of aromatic 
sulphides into sulphones.” 
It is known that organic sulphides may be converted first into 
sulphoxides and then into sulphones by means of oxidising agents, 
nitric acid for instance. From the following observations it appears 
to what extent atoms or groups which oceupy an ortho-position in 
regard to the sulphur atom, render the latter unoxidisable. 
