2 
Transactions of the Boyal Society of South Africa. 
Many determinations of this coefficient have been made by 
astronomers at various parts and heights on the earth's surface. 
These determinations naturally vary with the conditions under which 
they were made. It is matter of common experience that out on the 
Karoo the stars shine far more brilliantly than they do in the neighbour- 
hood of Cape Town. 
In this uncertainty it seemed to me desirable to make a determination 
of the coefficient of absorption for this part of Cape Colony — the Eastern 
province. This paper is a brief and preliminary statement of a single 
determination made on the summit of one of the hills of the Winterberg 
Range. 
I shall divide my paper into three sections : — 
(1) A statement of the Problem. 
(2) Consideration of the Winterberg Observations. 
(3) Deductions therefrom. 
1. Statement of the Peoblem. 
I shall only deal with simple relations, and thus present the problem 
in its simplest form. 
a. 
Let- 
s' represent an observing station on the earth's surface, 
sa, s/3, sc different altitudes of a star when viewed from the station s, 
sa the height of the atmosphere, 
OS the radius of the earth, 
