﻿ATOMIC HEAT TO CRYSTALLINE FORM. 127 



various differences in color, density, solubility and figure which belong to dimorphous 

 bodies are produced ; but when the difference of arrangement extends to the chemical 

 constituents of these molecular groups, independent but isomeric bodies are produced."* 

 It would thus appear that isomorphism, dimorphism, polymorphism and isomerism 

 are immediately dependent upon a peculiar arrangement of atoms, and of molecules 

 composed of two or more atoms. From the inherent tendency to such arrangement, 

 probably results the binary method of combination in both the organic and inorganic 

 worlds. Now, from all the foregoing facts, we have seen that when bodies agree in 

 form and properties, they also approximate in atomic heat. When bodies assume two 

 or more forms, their chemical properties differ, as do also their atomic heat. Bodies 

 having the same composition, but differing in structure (as in all probability isomeric 

 bodies do), and consequently in properties, differ also in atomic heat. 



Throughout this series, a remarkable parallelism is evident, between atomic heat on 

 the one hand, and arrangement of atoms, and forms and properties of bodies on the 

 other. It is very generally true, that bodies having the same form, have also the 

 same properties ; and that difference of form is accompanied by corresponding differ- 

 ence in properties. Very probable is it, therefore, that not only form, but also color, 

 specific gravity, solubility, hardness, &c, are all dependent upon certain arrangement 

 of atoms. But the arrangement of particles, necessarily pre-supposes an arranging or 

 motor agent, which constitutes the ultimate physical cause of crystallization. As the 

 attractive force, so grandly displayed in the solar system, must ever be present and in 

 action among the planetary bodies of that system, that they may be retained in their 

 accustomed orbits ; so the atoms of a crystal require the continued presence and equal 

 action of the arranging power, to maintain them in that relative position necessary to 

 the preservation of the general form. Hence we infer, that the arranging cause must 

 be a motor power, and always present. Furthermore, if it can be shown that such an 

 agent exists in a crystal, a strictly logical method should prevent us from seeking else- 

 where for the cause of peculiar atomic arrangement, and all the physical phenomena 

 manifestly dependent upon it. 



Now we have seen that caloric is always associated with the ponderable matter of a 

 crystal, and that it is positively related to crystalline form, and hence, to arrangement 

 of atoms upon which form depends. It only remains to adduce some proof of its 

 efficient activity. The experiments of Fresnel,t Baden PowelLJ Addams§ and others 

 show conclusively that heat is self-repellant. Moreover, a careful analysis of the en- 

 tire series of phenomena, which, in the aggregate, constitute the natural history of 

 caloric, tends strongly to establish the fact that heat is a most powerful motor agent. 

 Indeed, the ancients, with very few exceptions, contended (vaguely, however, and un- 



* Elements of Chemistry, p. 231. | Annates de Chem. et de Phvs. 29, 57, 107. 



% Philosoph. Mag. 18, 415. § Gmelin's Chemistry, vol. i. p. 212. 



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