330 | REPORT—1905. 
THURSDAY, AUGUST 17. 
The following Papers were read :— 
1. On Star Streaming. By Professor J.C. Karteyn.—See Reports, p. 257. 
2. The Magnetic Survey of South Africa. 
By Professors J. C. Beatriz and J. T. Morrison. 
A survey of South Africa was started by Professors Beattie and Morrison in 
the summer of 1897-1898. 
The observational work has been carried on since that time whenever opportunity 
offered ; naturally it was greatly interfered with by the war. Soon after the 
declaration of peace the various South African Governments each contributed to 
a fund for paying the expenses of a field party for a year’s continuous work. 
This party observed during the whole of 1903 and part of 1904, 
Financial assistance has also been received from the Government Grant Com- 
mittee of the Royal Society. 
The necessary observations have been made at about 400 stations, distributed 
chiefly along the various railways in Cape Colony, Rhodesia, the Transvaal, the 
Orange River Colony, and Natal, in the south of Cape Colony, the east of the 
Transvaal, the Basutoland border, and the north-west of Cape Colony. 
Observations have been repeated at twenty widely separated stations for the 
purpose of determining the secular variations of the elements. 
The annual and the daily observations have been derived from the earlier work 
of Sabine in South Africa, 
3. The Radio-activity of Ordinary Matter! By A. Woon, B.A., B.Sc. 
4. Thermal Radiation at Very Low Temperatures. By J.T. Borromiey, 
LL.D., D.Sc., PRS. 
The experiments described in this paper form part of an investigation on which 
the author has been engaged for some time past. The object of this investigation 
is the direct determination, in absolute measure, of the loss of energy from a 
heated body to cooler surroundings under differing circumstances as to (1) the 
dimensions of the cooling body ; (2) the state of the surfaces cf the cooling body 
and of the containing envelope; and (3) the mean absolute temperatures of the 
cooling body and the envelope. Several papers have already been published by 
the author on this subject, some of them communicated to Section A of the 
British Association ; and when, through the extreme kindness of Lord Blyths- 
wood, an unlimited supply of liquid air was placed at the author’s disposal, to be 
followed by a supply of liquid hydrogen, it seemed most desirable to extend the 
research in the direction indicated, and to determine, in absolute measure, the 
radiation, under given circumstances, from a body at, say, ordinary atmospheric 
temperature, to an enclosure at a temperature which may perhaps approximate to 
that of space. So far as is known to the author nothing of this kind has hitherto 
been attempted. 
The following is a general description of the apparatus used. At the centre of 
a hollow sphere of copper, the interior surface of which has been-coated with a 
’ See Philosophical Magazine, ix. 1905, p. 550. 
