MATTER. 19 



accordingly, is the smallest portion of a body that is capable of existence 

 in a free state, and that, further, as a unit no longer exhibits the aggre- 

 gate condition. The molecule is, however, not the ultimate unit of the 

 body. On the contrary, every molecule consists of a collection of the 

 smallest units, which are known as atoms. An atom is incapable of 

 occurring alone in a free state, but atoms unite with other atoms of 

 the same or of different character to form atom-complexes, desig- 

 nated molecules. Atoms are unconditionally insusceptible of division; 

 whence the name. Atoms, further, are conceived to be of constant size 

 and solid in themselves. From the chemical standpoint the atom of an 

 elementary body (element) is the smallest amount of an element that 

 is capable of entering into chemical combination. Just as ponderable 

 matter consists in its ultimate parts of ponderable atoms, so also does 

 the ether, imponderable matter, consist of analogous particles of smallest 

 size, namely, ether-atoms. 



Within ponderable matter the ponderable atoms are arranged in 

 quite a definite order with relation to the ether-atoms. The ponderable 

 atoms are drawn mutually toward one another (attraction) ; the pon- 

 derable atoms likewise attract the imponderable atoms; but the ether- 

 atoms mutually repel one another. It thus comes about that in the 

 ponderable mass ether-atoms are collected about every ponderable atom. 

 These collections, designated "dynamids" by Redtenbacher, tend, in 

 accordance with the powers of attraction of the ponderable atoms, to 

 approach one another, but only so far as permitted thus to do by the 

 repellent power of the surrounding ether-atoms. Therefore the pon- 

 derable atoms can never cohere without interstices, but the entire mass 

 of matter must be considered as loose in texture in consequence of the 

 interposed ether-atoms, which prevent immediate contact between pon- 

 derable atoms. 



The aggregate condition of the body depends therefore upon the 

 mutual arrangement of the molecules (namely, those small particles of 

 matter that may still occur isolated in a free state). 



Within solid bodies, which are characterized by constancy of volume, 

 as well as independence of form, the molecules are arranged in a fixed 

 and unchangeable relation with one another. In fluid bodies, which are 

 characterized by constancy of volume, though by variability of form, 

 the molecules are in constant movement, just as in a mass of moving 

 worms or insects the individual animals are incessantly changing their 

 place with relation to one another. If this movement of the molecules 

 attains such proportions that the individual molecules scatter in all 

 directions (just as the moving collection of insects separates into its 

 constituent parts), the body becomes gaseous, and is characterized in this 

 form both by its inconstancy of form and its variability in volume. The 

 study of molecules and their motor phenomena is the part of physics. 



FORCES. 



Gravitation; Work of a Force. All phenomena appertain to 

 matter. They are the appreciable expression of the forces inherent in 

 matter. The'forces themselves are not appreciable ; they are the causes 

 of the phenomena. The first of the forces to be considered is gravita- 

 tion. According to the law of gravitation every particle of ponderable 

 matter in the universe attracts every other particle with a certain degree 



