204 T. S. Hunt on the Constitution 
position, is untenable. It was further asserted, that the simple 
relations of volumes which Gay Lussac pointed out in the chemi- 
cal changes of gases, apply to all liquid and solid species, thus 
leading the way to a correct understanding of the equivalent vol- 
umes of the latter. While chemists have not hesitated to assign 
high equivalents to bodies of the earbon series, they have been 
inclined to make the equivalent weights of denser mineral species 
correspond, to formulas representing the simplest possible ratios. 
We have endeavored from a consideration of the theory of equiv- 
alent volumes, to point out the errors to which this method has 
led, and to show that we must assign to most mineral species 
much higher equivalent weights than have hitherto been ad- 
mitted. 
It was further asserted, that a relation similar to that observed 
in the formulas of allied hydro-carbonaceous bodies, and desig- 
nated as chemical homology, exists in the formulas of mineral 
species. We have said that these formulas, deduced from the re- 
sults of analysis, are not to be looked upon as expressing any pre- 
existing relations in the constitution of the species, which is not 
to be regarded as a compound, but as an individual, in which the 
so-called chemical elements have no actual existence. The ar- 
the numerical relations which have been found to govern the 
transformations of the higher species. 
The formulas of homologous bodies may be represented as se- 
ries in arithmetical progression. The first term may be the same 
as the common difference, and the series is then 
b, 26, 3b...nb, 
as in the hydrocarbons C2H2, CsH;,CsHe, etc. If the first term 
is unlike the common difference, the series is. 
a, a+b, a+2b,...a+nb, 
of which the ammonias, NHs, NH3+C:H:, NH;+2C2H:, etc., 
are examples. Both of these cases are illustrated in the chem- 
ical history of mineral species. 
In the paper already referred to, it has been shown, from the 
relations of carbon, sulphur and oxygen on the one hand, and of 
hydrogen with the metals on the other, that M 2S2, M202, and 
H:;0O. (M representing any metal), may be compared with HzC2. 
This view will be applied in extending the application of the 
principle of homology. ‘The sesqui-oxyds like ferric oxyd, chro- 
mic oxyd, and alumina, will be regarded as oxyds of ferricum, 
chromicum, and aluminicum, having two-thirds the equivalents 
ordinarily assigned to these metals, and represented by fe, er and 
al, so that Fe2O., becomes 3feO, capable of replacing 3Mg0O, or» 
3FeO. In the same way arsenic and antimony in one-third theit 
usual equivalents may be represented by as, sb, and AsO» becomes 
