88 HISTORY OP THE EARTH. 
47. Prop. II. The primitive rocks toere first formed and 
consolidated, and their consolidation took place before the ex- 
istence of either plants or animals. 
The primitive rocks underlie the others, and the rock or stra- 
tum which rests upon another, must in general be the more recent 
of the two. To this conclusion we must at length arrive what- 
ever theory of the earth we adopt. If its original liquidity was 
produced by heat, there must in the first instance have been 
formed upon the surface of the molten flood, a substratum or floor 
for the deposits of succeeding times to rest upon. That crust of 
consolidated matter is a crystalline primitive rock, and though parts 
of it were afterwards broken and constituted the material for the 
mechanical aggregates of a later period, yet is it true that the 
most ancient transition stratum is of more recent origin than 
that on which it reposes. By some geologists, gneiss and mica slate 
are regaded as the most ancient of the rocks, as constituting the 
original crust that was first of all spread over the surface of the 
liquid mass. Beneath these a bed of granite was gradually pro- 
duced by the radiation of heat into the surrounding space, and 
above them in some instances, the transition and secondary strata. 
Where granite appears as it frequently does, at the surface, and 
at great elevations, upon the summits of mountains, it is not ne- 
cessary to suppose that it assumed its form and was consolidated 
in its present position. It may have existed as a rock beneath 
the general surface of the globe, and been raised, either gradually 
or during some great, convulsion, to the position in which we 
find it. 
As no organic remains of any kind are imbedded in the prim- 
itive rocks, we infer that they never contained any, and that they 
were consolidated before either plants or animals existed, it being 
improbable that if their consolidation was either coeval with or 
posterior to the existenceof organized beings, they would embrace 
no evidences of this fact. It is possible indeed that the favorite 
theory of some geologists is true, that organic remains once ex- 
isted in the materials from which these rocks were formed, and 
were destroyed by the action of fire or water during the fusion or 
solution they must have undergone before assuming the forms 
and characters they now exhibit, but no appearances have been 
observed which lend any degree of probability to this opinion, 
and there is a considerable probability against it. Commencing 
with the higher strata, the remains of every kind are numerous, 
as we descend, their number gradually, though not uniformly, 
diminishes, till in the transition class, we find only the remains 
of zoophytes — a race occupying the lowest place in the scale of 
living creatures. It was to be expected that this- descending se- 
ries would have a limit, where the traces of life whether animal 
or vegetable should cease altogether. Such a limit we find in 
the primitive rocks, and though it is possible that the strata in 
which we find no traces whatever of life, once teemed with liv- 
