466 



Mr. E. Wilson. 



the heavy metals. For instance, taking unity to represent the normal 

 volume, oxygen may assume the following volumes : — 1, 1^, If, 

 2 and 3 ; sulphur, ^ f , |-, 1 and 1^- ; and the halogens, ^ f , J, 



7 11 

 85 ± 4- 



In conclusion, it may be remarked that the tables lend their chief 

 support to proposition (3). Propositions (1) and (2) must be con- 

 sidered more hypothetical, but the writer wished to place them on 

 record, because, if true, they would afford a physical interpretation to 

 the fundamental numbers of column (IV) Table I. In proposition (1) 

 also is to be found an explanation of the allotropism of the elements, 

 carbon, silicon and phosphorus, based as it is upon the supposition that 

 these allotropic forms contain a different number of atoms in the nucleus 

 of their molecules with the same molecular volumes, and there are 

 independent physical reasons, which render it not improbable that the 

 accumulation of similar atoms in the nucleus of a molecule would not 

 alter its volume, whatever be the law of force in action. The question 

 is perhaps not altogether beyond the reach of direct experimental 

 investigation. For if experiments on interdiffusion could be carried 

 on at the temperature of gaseous mercury, the determination of the 

 molecular volume of monatomic mercury, by the method of Loschmidt, 

 would shed a very great deal of light on the subject. 



Note. — Let V be the volume of any solid or liquid substance, W its 

 weight, S its specific gravity, then 



V 



The unit of volume being the volume of the unit of weight of the 

 standard substance. 



For distinctness we will take the hydrogen atoms as the unit of 

 weight, and water at its greatest density as the standard substance. 

 Then 



TT , « , -, £ , weight of molecule H n 



Volume of molecule oi water = —2 . — — «_ =18, 



specific gravity of water 1 



or the unit of volume is part of the volume of the molecule of 

 water. 



Suppose the substance to contain n molecules, then — 



W 



c_ n 



Now — is the weight of one 'molecule, and we may define — as the 



n n 



volume of one molecule. 



