Explanation of the 11 Brownian" Movement. By W. N. Hartley. 9 
James Thomson showed to he due to alterations in surface tension 
consequent on evaporation of the spirit. 
By shaking arsenious acid with water, bubbles of air become 
incrusted with the powder and sink in the liquid. These are 
attracted * by a warm wire, and as they are of considerable size, no 
microscope is required to see them, as is the case with the bubbles 
in mineral cavities. 
* Since the approach of a bubble to a warm body is caused by the tension of 
the liquid behind it, the attraction is more apparent than real. 
