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XXXII. On Molecular Physics. By Prof. W. A. Norton. 



[Continued from p. 204."] 

 Molecular Constitution and Mechanical Properties of Bodies. 



EVERY body of matter consists of separate particles, or mole- 

 cules in a state of equilibrium under the action of the forces 

 proper to the particles, or of these in connexion with extraneous 

 forces taking effect upon the particles. The interstices between 

 the molecules we conceive to be pervaded by both the electric 

 and the universal sether, having probably different densities in 

 different substances. The state of equilibrium in which each 

 particle of the mass subsists, implies that the effective forces 

 acting upon it, from opposite sides, are equal and directly op- 

 posed, or else that the effective forces of each side are equal to 

 zero. The different mechanical properties of different sub- 

 stances may be ascribed, primarily, to differences in the value 

 of the ratio of the constants of electric attraction and repulsion 



(, in Table LI: and to a certain extent also to differences in 

 m' ) 



the size of the molecular atmospheres, upon which the value of 



k in Table I. partly depends. In consequence of these sup- 



posed differences in the value of the ratio — , each substance 



should have its own special curve of molecular action. It is 

 natural to suppose that the constant n of the force of attraction 

 exerted by the atom upon its atmosphere would in general increase 

 with the mass of the atom, and so that the force of cohesion would 

 be greatest in those substances whose atomic weights are the 

 greatest. But as we cannot affirm that the weight of an atom 

 must necessarily be proportional to the force of attraction ex- 

 erted by it upon its electric atmosphere, and as the constant m 

 may also be subject to variations, substances of nearly equal 

 atomic weights (e. g. } gold, platinum, bismuth, and lead) may 

 have different properties. 



The molecules of a substance in the solid state may be aggre- 

 gated together as a homogeneous mass, or in groups more or less 

 complex. The mechanical properties of the mass vary with the 

 mode of aggregation. The form of aggregation assumed, in the 

 process of solidification, depends upon the circumstances, with 

 respect to cooling, pressure, &c, under which the solidification 

 occurs. The effect of the same circumstances should vary with 

 different substances, with their properties in relation to heat ; but 

 these properties are primarily dependent upon the general fea- 

 tures in the constitution and condition of the molecules, upon 



