Mr. Whelpley on the Idea of mi Atom. 367 



Chemical combination. 



The idea of cohesion is that of a resoUition into forces, which 

 act at the extremities of the three axes of the nucleus. Single 

 atoms must have but one centre. Let a nucleus of gaseous chlo- 

 rine be nearly in contact with one of hydrogen. Let them be 

 together as part of a chain of mutually electrified nuclei : then, 

 let them be affected, and affect each other, to that degree that 

 solid axes are generated in them. They will then cohere ; but 

 this is not like common cohesion — for, becoming instantly gas- 

 eous by the heat developed about them, they remain in com- 

 bination, and act, as though they were a simple atom, with a 

 single set of axes. To form an idea of such an atom, we may 

 suppose that different elementary atoms, chlorine, hydrogen, 

 &c., are affected in different degrees, by the same cause. For, 

 if it is supposed that crystalline cohesion is an effect that can 

 happen only between atoms in every respect equal and alike, (as 

 is certain by the idea already given of it,) the mode of combina- 

 tion between unlike atoms will be different from cohesion, in the 

 degree of their unlikeness. Suffice it to say, that this difference 

 consists, probably, in a nearer approach of the centres of the two 

 atoms, and in the formation of an ellipsoidal, or spheroidal, 

 compound nucleus, by the resolution of the two systeins of poles 

 into one system, enabling them to act as a single atom.* A 

 fuller exposition of this and other points of the atomic theory, is 

 reserved for more leisure. 



Recapitulation. 



The idea of an atom, like that of an element, must satisfy 

 all the conditions of time, space, and number; and must be 

 composed of two forces which originate from a common prin- 

 ciple, or substratum ; and since that principle fills all space, the 

 powers of the atoms, which are formed by its resolution from 

 certain centres, may extend through all space. An atom, there- 

 fore, is in a material sense omnipresent. The two forces into 

 which an atom resolves itself, if they develope each other, are 

 necessarily equal ; they operate from the extremities of the di- 



* I am sustained in this view by the crystallographic hypothesis of Mr. J. D. 

 Dana, as it is given in his Mineralogy. He supposes, that compound molecules 

 are spheroidal or ellipsoidal, like the nuclei of simple atoms. 



