Page:The evolution of worlds - Lowell.djvu/184

152 while. We only know what he would have been worth had he followed our advice in the matter of investments and lived as frugally as we recommended. For here, too, we are obliged to make certain assumptions. Nevertheless the figure obtained in the case of the planets' stores of heat is so enormous as to leave a most ample margin for dissipation. Had the Earth contracted from a fairly generous expansion to its present state under the probable law of density suggested by Laplace in another connection, the heat developed would have been enough to raise the whole globe to 160,000° F. if of iron, 90,000° F. if of stone. As 10,000° F. would have sufficed for the Earth to have kept up its past, to say nothing of its present, state, we are justified of our deduction.

Nor is the Earth the only body in the system which thus argues itself evolved by the falling together of its present constituents. In the larger planets Jupiter and Saturn we seem to see the heat, far as we are away. For the cherry hue they disclose between their brighter belts proves to come from greater absorption there of the green and blue rays of the spectrum, indicating a greater depth of atmosphere traversed. Thus these parts lie at a lower level, and their ruddy hue is just what they should show were they still glowing with a dull red heat.

Heat is not only the end of the beginning, it is the be