conditions. A stage lower in degree of
composition we come to the vast assemblage of oxy-hydro-carbons, numbers
of which show many and decided affinities, and are stable at common
temperatures. Passing to the inorganic group, we are shown by the salts
&c. strong affinities between their components and unions which are, in
many cases, not very easily broken. And then when we come to the oxides,
acids, and other binary compounds, we see that in many cases the
elements of which they are formed, when brought into the presence of one
another under favourable conditions, unite with violence; and that many
of their unions cannot be dissolved by heat alone. If, then, as we go
back from the most modern and most complex substances to the most
ancient and simplest substances, we see, on the average, a great
increase in affinity and stability, it results that if the same law
holds with the simplest substances known to us, the components of these,
if they are compound, may be assumed to have united with affinities far
more intense than any we have experience of, and to cling together with
tenacities far exceeding the tenacities with which chemistry acquaints
us. Hence the existence of a class of substances which are
undecomposable and therefore seem simple, appears to be an implication;
and the corollary is that these were formed during early stages of
terrestrial concentration, under conditions of heat and pressure which
we cannot now parallel.

Yet another support for the belief that the so-called elements are
compounds, is derived from a comparison of them, considered as an
aggregate ascending in their molecular weights, with the aggregate of
bodies known to be compound, similarly considered in their ascending
molecular weights. Contrast the binary compounds as a class with the
quaternary compounds as a class. The molecules constituting oxides
(whether alkaline or acid or neutral) chlorides, sulphurets, &c. are
relatively small; and, combining with great avidity, form stable
compounds. On the other hand, the molecules constituting nitrogenous
bodies are relatively vast and are chemically inert; and such
combinations as their simpler types enter into, cannot withstand
disturbing forces. Now a like difference is seen if we contrast with one
another the so-called elements. Those of relatively-low molecular
weights--oxygen, hydrogen, potassium, sodium, &c.,--show great readiness
to unite among themselves; and, indeed, many of them ca