( 465 ) 
only those grains were measured which were passing through the 
very middle of the field. 
Of specimen VI the size of the grains could not be fixed, the 
matter for the. greater part (90°/,) being too coarse to be treated in 
that way; a proper set of sieves not being at my disposal. 
The result of the examination as to the size of the grains is 
graphically shown in the additional table. 
Grouped together were grains up to the size of 0.05 mM., those 
from 0.05 to 0.10 mM. ete. From this table appears that in specimen IT 
the average size of the quartz-grains considerably exceeds that of 
the heavy minerals, although, in a smaller degree, specimen IT] 
shows forth the same, whereas in specimen IV there appears to be 
no difference in the average size of the grains; also in specimen V 
we can hardly speak of a moving apart of the two lines. Specimen I 
is left out of consideration, because, on account of the irregular 
quartz-line, no conclusion can be drawn as to its average size. 
Judging from the abundant quantity of Amphibole; from the low 
percentage of heavy minerals and from the sharp edges of the grains 
it seems not presuming too far to consider the examined sands, a 
deposit of the ice. The influence of water however cannot be denied for 
how otherwise can be explained the presence of so many fragments 
of shells and the washed character of specimens II and III. From 
the graphical table, one feels inclined to conclude that the influence 
of the water has been greater on the surface than deeper down. 
It is to be regretted that no specimen has been kept of the upper 
sand. Now we miss for our comparison, a purely alluvial sand formed 
on that spot. 
s-Gravenhage, 21 Februar 1902. 
Astronomy. — ‘The relation between the brightness of a luminous 
point and the moments at which we observe its sudden 
appearance or disappearance.” By Prof. H. G. VAN DE SANDE 
BAKHUYZEN. 
At the meeting of the Royal Academy May 29% 1886 I read a 
paper on researches made to determine the influence of the brightness 
of a luminous point on the moments at which we observe its sudden 
appearance. ‘These researches have later been continued and in the 
“Archives Néerlandaises” Serie II, Vol. VI, p. 727 the results of 
all these observations have been published, together with an explana- 
tion of the fact that a great many astronomers observe the transits 
