From an attentive examination of these considerations, I am induced to conclude, that the interior of the sphere may be as well lighted as the exterior; or at all events, if not favoured with so great a degree of light at all times, it has a more regular and constant supply. But, admitting every thing on this subject that the opponents of the theory can suggest, I still discover no substantial reason why the earth may not be a hollow sphere. I can see no substantial reason why the inhabitants of that portion of the earth, (if any exist there) should be furnished with as great a degree of light, and as intense a heat, as we have upon the convex part of the sphere. Must it of necessity follow, that it cannot be inhabited, or if inhabited, that the beings who people its surface, are less happy than we? Certainly not. Is it not well known to us, that every grade and species of animals, under every variety of circumstance, whether inhabiting the air, the earth, or the water, are fitted by an all-wise Providence to their several conditions, and mediums, in which they reside? As well might we conclude, that the immense planet Jupiter, situated so far from the sun as he is, can be nothing but a dark, cold, and barren waste, unfitted for the residence of intelligent beings. It is ascertained by calculation, that the light and heat which Jupiter receives from the sun, is only the one twenty-seventh part of what the earth receives.[41] The light and heat which Saturn receives from the sun is estimated at only the one hundredth part of that of the earth;[42] and the planet Georgium Sidus, revolving such an immense distance further from the sun, than either of them, must enjoy still less light and heat; according to which, we would conclude, (if we adopt the belief, that the degree of light and heat, to which we are accustomed, is necessary for the support of life,) that those vast planets are not fitted by the God of nature for the residence of intelligent beings; however, I am inclined to believe that both light and heat are communicated to them, in some way not well known to us, sufficient for the purpose. The true principles of light and heat, and the manner in which they are generated and transmitted, are not perhaps yet well understood and defined.[43]