I 
62 Mr. Christie on the effects of temperature on 
be most necessary. ' There would be no difficulty in this 
reduction, if we could ‘give in terms of the intensity of any 
magnet the increment or decrement of intensity correspond- 
ing to a certain decrement or increment of temperature at all 
temperatures. To determine this accurately, would however 
require a great variety of experiments to be made with 
magnets of very different intensities ; but as I have not made 
these, I must content myself for the present with pointing 
out some of the facts which I have ascertained from more 
extended experiments than those I have already given, re- 
serving the detail of these experiments for another oppor- 
tunity, should they be deemed of sufficient interest. 
These experiments were made with a balance of torsion, 
the needle being suspended by a brass wire inch in 
diameter : by them I ascertained the following facts : 
1. Commencing with a temperature — 3° Fahrenheit, up 
to a temperature 127°, as the temperature of the magnets 
increased, their intensity decreased. Owing to the almost 
total absence of snow during the winter, I was unable to re- 
duce lower the temperature of the large magnets which I 
made use of ; but from an experiment I made at the Royal 
Institution, in conjunction with Mr. Faraday, in which a 
small magnet, enveloped in lint well moistened with sul- 
phuret of carbon, was placed on the edges of a basin con- 
taining sulphuric acid, under the receiver of an air pump, I 
found that the intensity of the magnet increased to the lowest 
point to which the temperature was reduced, and that the 
intensity decreased on the admission of air into the receiver, 
and consequent increase of temperature in the magnet. This 
