84 
the peculiar movements of these particles appear like elec- 
trical attraction and repulsion, similar movements might 
be caused by the changes of temperature of the particles, 
transmitted through the solutions. 
“ On a General System of Numerically Definite Reason- 
ing,” by Professor William Stanley Jevons, M.A. 
The system of numerical reasoning described in this paper 
arises from the combination of arithmetical or algebraical 
calculation with logical reasoning. Its purpose is to deter- 
mine as far as possible the numbers of individual objects 
which may compose classes or groups of objects under any 
given logical conditions, the data consisting in those logical 
conditions and the numbers of individuals in certain other 
related classes. 
