ACADEMY OF SCIENCES. 99 
strata which constitute the crust of the earth, form a gauge of relative time, 
for which human chronology scarcely affords a unit of measure. It is per- 
fectly certain that during the cretaceous epoch, a comparatively recent period 
in the world’s history, none of the physical features existed, which mark the 
the present surface of the globe. Continents have undergone movements of 
elevation and depression, their shore lines sunk under the ocean, and sea- 
beaches have been transferred far into the interior of pre-existing continents. 
All dry land has been submerged, excepting recent volcanic products and 
metamorphosed rocks. These introductory facts are necessary to ethnological 
research. 
A cooling sphere, having acquired a solid crust around a nucleus of fiery 
liquid, in parting with its heat by radiation into space, must contract, distort- 
ing its outward surface by pressure, raising mountain ridges, and depressing 
corresponding valleys, where the first seas became located. Sun and moon, 
obedient to the law that bodies move to each other in proportion to their 
masses, and inversely as the squares of their distances, attracted tidal move- 
ments in molten fluids under the crust, in hot salt seas, and the thick unre- 
fined atmosphere above. Fluids as well as other matter were more gross 
during their primitive states. Rupture and re-formation succeeded one 
another, until the primitive igneous period of angular azoic granite, became 
sufficiently hardened to withstand the ordinary pressure of inward forces, 
gradually preparing to furnish physical conditions, suitable to begin the evo- 
lution of animal lifein its most elementary forms, corresponding with the 
imperfect condition of existing elements. 
During the mighty struggles of the unrefined elements, internal convulsions 
sent the hot salt sea surging over a large portion of the surface, and sediment- 
ary deposits formed new stratifications. Substances impregnating the waters 
united in forming cry-tals. The waters, having raged from point to point, 
were obliged to seek an equilibrium, and retired to the valleys, forming vari- 
ous oceans, seas, lakes, and rivers. 
In the early carboniferous period which succeeded, the extra nitrogen and 
carbon were rapidly absorbed from the air, and the density of all exterior 
elements greatly reduced. A period was thus established, where, under fa- 
vorable auspices, and in limited localities, the very imperfect initiatorial 
orders of vegetable and animal life appeared. Aninfinity of embryo existences 
are contained within the crust of the earth, awaiting the slow process of 
development. Life generated at the initial period was of the very lowest 
order, unable to support or reproduce itself to any considerable extent. 
From this threshold of progression, conditions became sufficiently advanced 
to admit of the systematic reproduction of species; the age of spontaneous 
generation having performed its limited duty in the general ripening of the 
globe, may have ceased and passed away with conditions which sustained it, 
and matter, within itself, matured the power to reproduce its kind, endowed 
with a progressive principle, destined eventually to evolve its ultimates. 
This hypothesis explains why spontaneous generation may have had its day 
and subsequently ceased. 
Crinoides, conchiferce, crustacea, polypi, and polyparia successively appear 
as elements are advanced to the necessary conditions to sustain such forms of 
