723 
communication we find for the average parallax of the stars of the 
magnitude m in front of the absorbing screen: 
PL 
1 
En i 0,40 — rn (m— My — ¢)?— Ee (e — po)? 
ie —— fro do. 
The same integral taken between the limits + so represents the 
normal value of A, zin. If we put, therefore 
we = 0,22 0, — 1,078 — 0,132 (m — 9) = a, + 0,452 
and 
% 
al 
ix loge AOS i dt=7; 
then 
ae Ys 
x ne 
The average proper motions are enlarged in the same proportion 
as the average parallaxes. For y,= 6,05, r=160 parsecs (this 
value has been taken, because it allowed us to use the numbers of 
the previously calculated tables), we get for 
nw ==. 0 ‘ 8 9 
mee 1 Ae CRE 2, 
Dyson and Merorrr in their article have already compiled the 
proper motions of the stars in the darkened regions of Taurus, and 
have established, that they are not greater than anywhere else. We 
find, indeed, for their average 0",044, whilst stars of that magnitude 
(1 of the 6, 1 of the 7, 5 of the 8", 9 of the 9 magnitude) 
at such a galactic latitude give a normal average of 0".041. For 
the small number of stars the negative conclusiveness of this result 
is not strong enough in itself to refute the existence of an absorbing 
nebula. Of a greater average speed, however, through the effect of 
a gigantic attractive mass, there is no trace. 
§ 3. The difficulties, and as yet unconfirmed consequences, result- 
ing from the assumption, that the star-voids in Taurus are caused 
by absorbing gas-masses, give rise to the question, as to whether 
no other explanation is possible. Barnarp has always emphasized 
the fact that not all dark spots and regions in the Galaxy are to 
be attributed to absorption, but that a great number of them are 
undoubtedly due to actually void space. In many cases the aspect 
; 47 
Proceedings Royal Acad. Amsterdam. Vol. XXIII. 
