595 



and immediately cease on the cessation of that power. Thus do 

 these two modes of action stand in the same general antithetical re- 

 lation to one another as the positive and negative conditions of elec- 

 tricity, the northern and southern polarities of ordinary magnetism, 

 or the lines of electric and of magnetic force in magneto-electricity. 

 Of these phenomena, the diamagnetic are the most important, from 

 their extending largely, and in a ncAv direction, that character of 

 duality which the magnetic force was already known, in a certain 

 degree, to possess. All matter, indeed, appears to be subject to the 

 magnetic force as universally as it is to the gravitating, the electric, 

 the cohesive and the chemical forces. Small as the magnetic force 

 appears to be in the limited field of our experiments, yet when 

 estimated by its dynamic effects on masses of matter, it is found to 

 be vastly more energetic than even the mighty power of gravitation, 

 which binds together the whole universe : and there can be no 

 doubt that it acts a most important part in nature, and conduces to 

 some great purpose of utility to the system of the earth and of its 

 inhabitants. 



Towards the conclusion of the paper, the author enters on theo- 

 retical considerations suggested to him by the facts thus brought to 

 light. An explanation of all the motions and other dynamic phe- 

 nomena consequent on the action of magnets on diamagnetic bodies 

 might, he thinks, be offered on the supposition that magnetic induc- 

 tion causes in them a state the reverse of that which it produces in 

 magnetic matter : that is, if a particle of each kind of matter were 

 placed in the magnetic field, both would become magnetic, and each 

 would have its axis parallel to the resultant of magnetic force pass- 

 ing through it; but the particle of magnetic matter would have its 

 north and south poles opposite to, or facing the contrary poles of 

 the inducing magnet ; whereas, with the diamagnetic particles, the 

 reverse would obtain; and hence there would result, in the one 

 substance, approximation ; in the other, recession. On Ampere's 

 theory, this view would be equivalent to the supposition that, as 

 currents are induced in iron and magnetics, parallel to those existing 

 in the inducing magnet or battery wire, so, in bismuth and other 

 diamagnetics, the currents induced are in the contrary direction. 

 As far as experiment yet bears upon such a notion, the inductive 

 effects on masses of magnetic and diamagnetic metals are the same. 



January 15, 1846. 



The MARQUIS OF NORTHAMPTON, President, in the Chair. 



James B. Neilson, Esq. was elected a Fellow of the Society. 



" On the Viscous Theory of Glacier Motion." By James D. 

 Forbes, Esq., F.R.S. &c. Part II. " An attempt to establish by 

 observation the Plasticity of Glacier Ice." 



