OEGANIO MATTEE. 7 



parac3'anogen, formed of tlie same proportions of these ele- 

 ments in higher multiples (N'a Cs), we have a solid which does 

 not fuse or volatilize at ordinary teniperatures. Lastly, 



in the most important member of this group, water, (H O 

 or else as many chemists now think Hj O2) we have a com- 

 pound of two incondensible gases which assumes both the 

 fluid state and the solid state within ordinary ranges of 

 temperature ; while its molecular mobility is still such that 

 its fluid or solid masses are continually passing into the form 

 of vapour, though not with great rapidity until the temper- 

 ature is raised to 212°.* 



Considering them chemically, it is to be remarked of 

 these binary compounds of the four chief organic elements, 

 that they are, on the average, less stable than binary com- 

 pounds in general. Water, carbonic oxide, and carbonic 

 acid, are, it is true, difficult to decompose. But omitting 

 these, the i;sual strength of union among the elements of the 

 above-named substances is low considering the simplicity 



* This immense loss of molecular mobility wbich oxygen and hydrogen un- 

 dergo on uniting to form water — a loss far greater than that seen in other binary 

 compounds of analogous composition — suggests the conclusion that the atom of 

 water is a multiple atom. Thinking that if this conclusion be true, some evidence 

 of the fact must be afforded by the heat-absorbing power of aqueous vapour, 

 I lately put the question to Prof. Tyndall, whether it resulted from his ex- 

 periments that the vapour of water absorbs more heat than the supposed sim- 

 plicity of its atom would lead him to expect. I learned from him that it Aoa an 

 excessive absorbent power — an absorbent power more like that of the complox- 

 atomed vapours than like that of the simple-atomed vapours — an absorbent 

 power that therefore harmonizes with the supposition that its atom is a multiple 

 one. Besides this anomalous loss of molecular mobility and this anomalous heat- 

 absorbing power, there are other facts which countenance the supposition. The 

 unparalleled evolution of heat during the combination of oxygen and hydrogen is 

 one. Another is that exceptional property which water possesses, of beginning to 

 expand when its temperature is lowered below 40° ; since this exceptional property 

 is explicable only on the assumption of some change of molecular arrangement — a 

 change which is comprehensible if the molecules are multiple ones. And yet a 

 further confirmatory fact is the ability of water to assume a colloid condition ; for 

 as this implies a capacity in its atoms for aggregating into high multiples, it 

 suggests, by analogy with known cases, that they have a capacity for aggregating 

 into lower multiples. 



