The Poetry of Science; or, Studies of the Physical Phenomena of Nature

by Robert Hunt

HEAT—SOLAR AND TERRESTRIAL.

Solar and Terrestrial Heat—Position of the Earth in the Solar System—Heat and Light associated in the Sunbeam—Transparency of Bodies to Heat—Heating Powers of the Coloured Rays of the Spectrum—Undulatory Theory—Conducting Property of the Earth’s Crust—Convection—Radiation—Action of the Atmosphere on Heat Rays—Peculiar Heat Rays—Absorption and Radiation of Heat by dissimilar Bodies—Changes in the Constitution of Solar Beam—Differences between Transmitted and Reflected Solar Heat—Phenomena of Dew—Action of Solar Heat on the Ocean—Circulation of Heat by the Atmosphere and the Ocean—Heat of the Earth—Mean Temperature—Central Heat—Constant Radiation of Heat Rays from all Bodies—Thermography—Action of Heat on Molecular Arrangements—Sources of Terrestrial Heat—Latent Heat of Bodies—Animal Heat—Eremacausis—Spheroidal State Cold—Condensation—Freezing—Theories of Heat—Natural Phenomena—and Philosophical Conclusion.

We receive heat from the sun, associated with light; and we have the power of developing this important principle by physical, mechanical, and chemical excitation, from every kind of matter. Our convictions are, that the calorific element, whether derived from a solar or a terrestrial source, presents no essential difference in its physical characters; but as there are some remarkable peculiarities in the phenomena, as they arise from either one or the other source, it will assist our comprehension of this great principle, if we consider it under the two heads.

Untutored man finds health and gladness in the warmth and light of the sun; he rears a rugged altar, and bows his soul in prayer, to the principle of fire, which in his ignorance he regards as the giver and the supporter of life. The philosopher finds life and organization dependent upon the powers combined in the sunbeam; and, examining the phenomena of this wonderful band of forces, he is compelled to acknowledge that the flame upon the altar—on the Persian hills,—was indeed a dim shadow of the infinite wisdom which abides behind the veil.

The present condition of our earth is directly dependent upon the amount of heat we receive from the sun. It has frequently been said, that if it were possible to move this planet so much nearer that orb that the quantity of heat would be increased, the circumstances of life would necessarily be so far changed, that all the present races of animals must perish; and that the same result would happen from any alteration which threw us yet further from our central luminary, when, owing to the extremity of cold and the wretchedness of gloom, all living creatures would equally fail to support their organization.

To move the earth nearer to, or more distant from the sun, is an impossibility; but it has been argued that those planets which are near to the sun must possess a temperature which would melt our solid rocks, and vaporize the ocean,—while Uranus and Neptune must, from their distance from the source of heat, have so small an amount, that water must become solid as the rock, and such an atmosphere as that of the earth exist as a dense liquid.

It will be shown that according to the physical condition of the material substances, so are their powers regulated of absorbing and retaining the heat which falls as a radiant power upon their surfaces. Heat rays, in passing through the attenuated medium of planetary space, lose none of their power—this we know from the fact that even the less dense upper region of the earth’s atmosphere takes from the solar rays but an exceedingly small quantity of heat. Therefore, whether a solar heat ray traverses through one million, or one hundred million miles of space, it still retains its power equally of imparting warmth to the solid matter by which it is intercepted. There is no law of variation as the inverse square of the distance of those radiating powers. Consequently, there is no reason why the physical conditions, alike of the nearest and the most remote planetary bodies, should not be so adjusted that they all enjoy that life promoting temperature which belongs to the earth.

All the objects around us are adapted to the circumstances of the earth’s position in relation to the sun, to which we are bound by the principle of gravitation; opposed to that centrifugal force which tends constantly to drive the moving planetary mass off from the centre of power. The balance maintains its perfect equilibrium, although we have one power constantly drawing the earth towards the sun, and the other as constantly exerting itself to move it off into space at a tangent to the orbit in which the planet moves. In our examination it will be found that one common system of harmony runs through all the cosmical phenomena, by which everything is produced that is so beautiful and joyous in this world.

Heat, and the other elementary radiant principles, are often combined as the common cause of effects evident to our senses. The warmth of the solar rays, and their luminous influence, are not, however, commonly associated in the mind as the results of a single cause. It is only when we come to examine the physical phenomena connected with these radiations that we discover the complexity of the inquiry. Yet it is out of these very subtle researches that we draw the most refined truths. The high inferences to which the analysis of the subtile agencies of creation leads us, render science, pursued in the spirit of truth, a great system of religious instruction.