Polytechnic Association. 875 



eific lieats of atoms are the same. The law is regarded as a direct 

 confirmation of atomic weights. 



4. Molecular ity. According to the atomic theory, chemical forces 

 are brought in equilibrium when atoms combine and form a molecule. 

 Every gas and every vapor, undecomposed, has a density proportional 

 to its molecular weight. All known molecular combinations and 

 combining proportions are in accordance with the atomic doctrine. 

 Decomposition by electrolysis affords some evidence that the con- 

 stituent parts of a molecule, which are simultaneously separated, are 

 proportionate to atomic weights. Moreover, the molecule is supposed 

 to possess polarity, which, under the attraction of cohesion, determines 

 its position in the process of crystalline accretion. Thus, symmetrical 

 solids result from the perfect likeness of their integrant parts. 



5. Atomic Combining Capacity. The modern doctrine of types and 

 substitutions is solely based on the individuality of the atom, without 

 which the whole fabric of typical structures must fall. 



6. Isomerism. The fact that bodies containing the same elements, 

 and in precisely the same proportions, exhibit different properties, has 

 been thus far accounted for only on the supposition that atoms are 

 differently arranged in each body. These differences in arrangement 

 depend not only on the relative position of atoms, but also on the 

 order, as to time, in which they combine ; for two or more atoms having 

 such precedence over others as to combine first, may, by that means r 

 form a radical of such permanence as to play the part of an atom. 

 Apart from the question of radicals, we may ascertain the number of 

 different bodies which can be formed from the same number of differ- 

 ent atoms, by an application of the mathematical law of permutations. 



7. Homogeneity. The uniformity of structure and appearance of 

 any element or chemical combination of elements furnishes the most 

 palpable proof of the identity in size and shape of those definite parts 

 which we designate as molecules. This homogeneity is retained under 

 different degrees of pressure, thus making it apparent that molecules 

 are not only identical in structure, but that they approach and recede 

 in precisely the same manner under the same conditions. 



Finally : The foregoing statement regarding the existence of atoms, 

 which are indivisible and indestructible under the present order of 

 things, does not preclude the supposition that the atom may be a 

 cluster of smaller particles held together by a powerful affinity, which, 

 when counteracted, would leave them free to move within a given 

 sphere. On this assumption, it is highly probable that the relative 

 position of such particles may modify the combining capacity of the 



