ORIGINAL TEMPERATURE OF THE EARTH. 
83 
can be accounted for in no other way. Heat may escape by 
raeliation. From tlie figure of tlic earth tliercfore, we infer not 
onlv' that it was originally Iluid, but that its Iluidity was produced 
by fusion. 
3. 'I'he same condition of things is further indicated by the 
crystalline structure exhibited by the primitive rocks and cspccial- 
ly by granite. Tlie constitution of the whole mass of some ofthese 
rocks, as (granite and gneiss,) and crystals imbedded in others, (as 
mica slate,) prove that at some time previous to their consolida¬ 
tion, the particles of which they are composed enjoyed freedom 
of motion, and liberty to arrange themselves in obedience to the 
laws b_v wliich their mutual afiinitiesare regulated and governed. 
At the points where granite comes into contact with gneiss, mica 
slate, clay slate, or another mass of granite, it is often seen to 
send out veins into tliose rocks, demonstrating that it is itself of 
more recent origin; that they, having been first consolidatetl, were 
rent aiul bi oken liy some of the forces that are active in the crust 
of the globe, and the granitic material of the vein injected in a melt¬ 
ed state into the fissure that was thus formed. (Sec. IS.) In the 
liquidity of the granite which constitutes a vein, is involved that 
of the mass from which it issues, and of which it is a branch, and 
in the formation of the granite of a vein by cooling from a state of 
igneous fusion, a similar origin of this rock wherever it is found. 
But as we have at present upon the earth no source of heat of 
sullicient jiower to melt the mountain ranges of granite that tra¬ 
verse the surface of the globe, we infer that their former fluidity 
depended ujion their original tem|ierature. 
4. The oi iranic remains thatare found imbedded in the seconda¬ 
ry and tertiary strata, prove that the higher latitudes at least, were 
once much warmer than at the present day ; that a climate ap¬ 
proaching to that of the equatorial regions, or perhaps even hotter 
than what now obtains in any part of the world, prevailed with¬ 
in the polar circles. The coal beds have evidently jiroceeded 
from tlie vegetation of the most ancient times. Butin the shales 
that accompany them, we find sometimes the plants themselves 
imbedded, and sometimes merely the impressions they left be¬ 
hind them u]ion the clay that has since been hardened into shale, 
whilst it was yet in a soft and yielding state. But these plants 
appear to hav.c been altogether difl'erent from those now inhabit¬ 
ing the countries in which the mines lie, and to have approach¬ 
ed ill their forms and mode of growth the arborescent ferns and 
other vegetables of tropical climates. In the Isle of Sheppy at 
the mouth of the Thames, the fruit or seed vessels of not less 
than 700 species of vegetables have been discovered, very few of 
which agree with any that are known to be now jiroduced upon 
the earth, and the greater part resemble more nearly in their form 
and mode of growth those that inhabit the torrid, than such as 
belong to the temperate zone. The remains of animals of those 
races which live only in the hottest climates, (the elephant, rhi- 
