We shall describe... the principal results of the prolonged action of the solar rays upon the terrestrial globe. ...The state of the mass has varied continually in proportion to the heat received. This variable... internal temperature... has approached... nearer to a final state... subject to no change. Then each point of the solid sphere has acquired, and preserves... a fixed temperature, which depends only on the situation of the point... The final state of the mass, the heat of which has penetrated all... parts, can... be compared to... a vessel which receives by openings at the top, liquid from some constant source, and permits exactly an equal quantity to escape by orifices.Thus the solar heat has accumulated in the interior of the globe and is... continually renewed.

This distinction of luminous and non-luminous heat, explains the elevation of temperature caused by transparent bodies.

The interposition of the air very much modifies the effects of the heat upon the surface of the globe. The solar rays traversing the atmospheric strata, which are condensed by their own weight [at decreasing altitudes], heat them very unequally; those which are rarest are likewise coldest, because they... absorb a smaller part of the rays. The heat of the sun... in the form of light, possesses the property of penetrating transparent solids or liquids, and loses this property... when by... terrestrial bodies, it is turned into heat radiating without light.

Liquids are very poor conductors of heat; but they have, like aeriform media, the property of carrying it rapidly in certain directions. This is the same property which, combining with, combining with the centrifugal force, displaces and mingles all parts of the atmosphere... [and] ocean, and maintains in them, regular and immense currents.

The earth would have only the same temperature as the heavens, were it not for two causes... One is the internal heat... possessed at its formation... only dissipated through the surface; the other is the continued action of the solar rays... which produce at the surface, the diversities of climate.

The solar system is situated in a region of the universe, every point of which has a common and constant temperature, determined by the rays of light and heat which proceed from the surrounding stars. This low temperature is a little below that of the polar regions of the earth.

The heat of the earth is derived from three sources...1. ...Solar rays; the unequal distribution of which causes diversities of climate.2. ...The common temperature of the planetary spaces; being exposed to the radiation from the innumerable stars which surround the solar system.3. The earth preserves in its interior that primitive heat which it had at the time of the first formation of the planets. ...We will show ...the principle features of these phenomena.

The question of terrestrial temperature, one of the most remarkable and difficult in natural philosophy... I have... condensed in a single essay... the results of this theory. The analytical details... I have already published. I was specially desirous of presenting... a complete view of the phenomena and the mathematical relations... between them.

Profound study of nature is the most fertile source of mathematical discoveries.

If we consider further the manifold relations of this mathematical theory to civil uses and the technical arts, we shall recognize completely the extent of its applications. It is evident that it includes an entire series of distinct phenomena, and that the study of it cannot be omitted without losing a notable part of the science of nature. The principles of the theory are derived, as are those of rational mechanics, from a very small number of primary facts, the causes of which are not considered by geometers, but which they admit as the results of common observations confirmed by all experiment.