Such may be this endless circle, such this unbroken chain, binding together all beings in nature, and passing from the visible to the invisible world.
To those persons who may declaim with severity against the system which we have ventured to put forward, we shall put a question which cannot fail to embarrass them, for science has never been able to solve it. We shall ask them how the light of the sun, and the heat which results from it, are maintained? It is evident that the enormous quantities of heat and light which the sun sends out in torrents into space, must come from a source which cannot be inexhaustible, which has need of renewal, otherwise the sun would become extinct. As there is no effect without a cause, it is plain that the inconceivable quantity of forces which the sun distributes by his burning rays, must be derived from some place. M. Guillemin, in his work on the sun, passes in review the different theories which have been adopted, up to the present day, to explain solar radiation. The following is an analysis of a chapter of M. Guillemin's work on the "Maintenance of Solar Radiation."
Pouillet has calculated that if the sun were not supplied with something to make up for the losses he sustains, he must cool at the rate of one degree in a century. But this calculation falls short of the truth. Pouillet supposed that the specific heat of the sun is the greatest which can be conceived. The specific heat of the sun is, it is true, unknown, but instead of placing it at the maximum power, which it is not proved to be, we might suppose it, by an allowable hypothesis, to be equal to that of water, which is well known. Now if we grant to the sun the specific heat of water, we rectify Pouillet's calculation, and we arrive at the conclusion that the sun, if not furnished with any resources from which to repair his losses, would be entirely extinct at the end of 10,000 years. Professor Tyndall, whose experiments are more recent than those of Pouillet, and inspire greater confidence, says: "If the sun were a block of coal, and it were supplied with sufficient oxygen to enable it to burn at the degree of heat proper to that star, it would be entirely consumed at the end of 5000 years." Now the sun has existed for millions of years, for the transition periods of our globe, in which the first living beings were manifested, are traced back to millions of years. And yet his heat has not sensibly diminished since those distant ages. The proof that it has not diminished, is that the climates of the globe at the present time are the same as they were in the tertiary or quaternary epoch. In the tertiary or quaternary strata the same plants and the same animals which exist at present are found. Speaking of times nearer to our own, we may observe that the productions of the soil remain unchanged during the 2000 or 3000 years, whose traditions and historical archives we possess.