of Edinburgh, Session 1871 - 72 . 
603 
Monday , 15tli January 1872. 
Professor KELL AND, Vice-President, in the Chair. 
The following Communications were read:— 
1. On the Delation of Magnetism to Temperature. (With 
a Plate.) By D. H. Marshall, Esq., M.A., Assistant to the 
Professor of Natural Philosophy. Communicated by Pro¬ 
fessor Tait. 
The following was the arrangement adopted in these experi¬ 
ments :—A large magnet was put into a copper pot containing oil, 
which was heated up by a brass Bunsen, and its temperature deter¬ 
mined by a mercurial thermometer immersed in it. The magnet 
was set magnetically east and west, and placed so as to act 
with equal force on the poles of a small magnet, whose centre 
was in the prolongation of its axis. This small magnet was 
cemented to the back of a small concave mirror, suspended by a 
single silk fibre, and placed in a glass case to guard it against cur¬ 
rents of air. The deflections of the small magnet were measured 
exactly as in the reflecting galvanometer, and since from the nature 
of the arrangement, the absolute magnetism in the large magnet is 
directly as the tangent of the angle of deflection of the small one, 
its amount for any temperature was immediately measured by the 
reading on the scale. 
iE 
m \ 
(x + ly) 
N S, the poles of the fixed magnet, m its absolute magnetism. 
N a = x , SN = 1. The couples indicated are those produced by 
the large magnet, and the^earth’s magnetism, E, on the small 
magnet. 
