316 PKlXni'LKS OF CHK-MISTKY 



With the establishment of the law the conception of the molecule 

 was fully denned, and from it the conception of the magnitude of the 

 atom of elements. 



The particle or chemical particle or molecule must le consi'l' /"/ O8 

 the quantity of a substance entering into chemical rwrfiuii ////// <tth-r 

 molecules, and tuhich in a state of vapour occupies the same voIn/) at 

 two parts by weight of hydrogen. 



The molecular weight (which has been indicated by M) of a sub- 

 stance is determined by its composition, transformations, and vapour 

 density. 



The molecule is not divisible by the mechanical and physical 

 changes of substances, but in chemical reaction it is either altered in 

 its properties, or quantity, or structure, or in the nature of the move- 

 ment of its parts. 



An agglomeration of molecules, which are alike in all chemical 

 respects, makes up the masses of definite homogeneous substances in all 

 states. 19 



Molecules consist of atoms in a certain state of distribution and 

 movement, just as the solar system 20 is made up of inseparable parts 

 (the sun, planets, satellites, comets, &c.). The greater the number of 



19 A volume of gas, a drop of a liquid, or the smallest crystal, presents an agglomeration 

 of a number of molecules, in a state of movement, continuously repeated (like the stars of 

 the milky way), distributing themselves in order or forming their new systems. If the aggre- 

 gation of all kinds of heterogeneous molecules be possible in a gaseous state, where the 

 molecules are considerably removed from each other, then in a liquid state, where the 

 molecules are already close together, such an aggregation becomes possible only in that 

 aspect of mutual reaction between the molecules which appears in their chemical attrac- 

 tion, and especially in the faculty of heterogeneous molecules for combining together. 

 Solutions and other so-called indefinite chemical compounds should be regarded in this 

 light. According to the representation evolved in this work we should regard them as 

 containing both the compounds of the heterogeneous molecules themselves and the pro- 

 ducts of their decomposition, as in peroxide of nitrogen NoO4 and NOo. And we must 

 consider that those molecules A, which at a given moment are combined with B in AB, 

 will in the following moment become free in order to again enter into a combined form. 

 The instances of chemical equilibria proper to dissociated systems cannot be regarded in 

 any other sense. 



20 This strengthens the fundamental idea of the unity and harmony of the type of 

 creation which forms one of those ideas which impress themselves on man in all ages, 

 and give rise to a hope of arriving in time, by means of a lengthy labour of discoveries, 

 observations, experiments, laws, hypotheses, and theories, at a comprehension of the 

 internal and invisible structure of concrete substances with the same degree of clearness 

 and exactitude as has been attained in the visible structure of the heavenly bodies. It 

 is not many years ago since the law of Avogadro-Gerhardt took root in science. It is 

 within the memory of many living scientific men. It is not surprising, therefore, that as 

 yet little progress has been made in the province of molecular mechanics ; but the theory 

 of gases alone, which is intimately connected with the conception of molecules, show-- l<y 

 its success that the time is approaching when our knowledge of the internal structure of 

 matter will grow rapidly. 



