MAOKIE — ON TIIK HOTTOM-HOCKS. 167 
the riso of the range of internal heat beneath sedimentary masses. 
Were the old gneissic and granitoid rocks, that form the real nucleus 
of our present lands, generated, expanded, and uplifted on these prin- 
ciples and by those means 1 The evidence seems to incline towards 
this belief ; and if so, there must have been a world of land and sea 
older than those remote ancestral island-domes and ridges that form 
the earliest recognized traces of our present lands. For there must 
have been lands to have furnished the materials of those sediments, 
the heaping-up and over-piling of which gave increased range to the 
subterranean heat ; and there must have been waves and ocean-cur- 
rents to have abraded and worn them down, and to have transported 
their finely divided particles into the abyss. And this still older 
world-crnst — whether life-less or life-full — has been melted up by 
fervent heat, and fused into the adamantine foundations of the " ever- 
lasting hills." 
Tt is not, however, on the ancient physical geology of our globe 
that we wisii to dwell at length in tliese chapters ; our object is to 
treat more at large of the successive forms of the organized creatures 
which have inhabited it, and to portray in our descriptions and illus- 
trations the whole of the common forms of those abundant tribes 
whose offices have been the most important in the past conditions of 
our planet, and whose remains are charactei'istic of our principal rock- 
masses. 
Still, we could not avoid considering, first, the formation and uprise- 
of those ancient lands of which these perished beings were the in- 
habitants. Our thoughts must naturally first turn to the soil, the 
shape and extent of the land, the form and elevation of the hills, the 
flow of the rivers, if any existed, to the rivulets and rills, to the beat 
of the waves on the shore, to the sunshine, the rain, and the dew ; 
and then we seek to reclothe those ancient lands with plants, herbs, 
and trees, to bedeck them with flowers, and to repeople them with 
living creatures. Before we describe the first fossils we must think 
of the first land and the first water that trickled over its surface. 
We must think of the sky and the air, the sunshine and shadows, the 
storms and calms of that first age of terrestrial conditions. 
Philosophers tell us of a central heat, still suflRcient within the 
rs-.iige ')f 800 miles below to fuse (he most inlractable rock. Thfy 
