This indefatigable investigator of the heavenly phenomena shows, by many substantial proofs, drawn from natural philosophy, that _heat_ is produced by the sun’s rays only when they act on a calorific medium; and that they cause the production of heat by uniting with the matter of fire which is contained in the substances that are heated,--as the collision of flint and steel will inflame a magazine of gunpowder, by uniting with its latent fire, and bring the whole into action. This point is capable of a very clear elucidation. “On the tops of mountains, and at heights to which the clouds seldom reach to shelter them from the direct rays of the sun, we always find regions of ice and snow. Now if the sun’s rays themselves conveyed all the heat we find on the earth, it would of course be hottest in situations similar to the tops of mountains, where their course is least interrupted. But all those who have ascended in balloons confirm the coldness of the upper regions of the atmosphere; and, therefore, since even on the earth the heat of the situation depends on the facility with which the medium yields to the impression of the sun’s rays, we have only to admit, that, on the sun itself, the fluids composing its atmosphere, and the matter on its surface, are of such a nature as not to be capable of any excessive heat from its own rays. It is also a well known fact, that the focus of the largest burning lens thrown into the air, will occasion no heat in the place where it has been kept for a considerable time, although its powers of exciting heat, when proper bodies are exposed to it, should be sufficient to melt or fuse the most refractory metals.” That the sun is a luminous, and not an igneous body, has met with the general consent of modern philosophers; an opinion to which every new discovery in philosophy gives additional support. The telescope, said to have been invented by the children of a spectacle-maker at Middleburgh, in the year 1590, but first brought to such a degree of perfection by Galileo as to make any considerable discoveries in the celestial regions, has led to the most important results in the science of astronomy. Among which are the _spots_ in the sun’s disk, by whose motion from west to east the sun is perceived to revolve upon his own axis in 25 days, 14 hours, 8 minutes. This revolution of the sun round his own axis is probably not the only motion which this luminary experiences. There is great reason to believe that he has another motion, either rectilinear, or round some indefinitely remote centre of attraction. In this last course, he carries along with him, through space, the entire system of planets, satellites, and comets; in the same manner in which each planet draws his satellites along with him in his motion round the sun. He communicates light and heat to at least twenty opaque bodies, which revolve round him, at different distances, in ellipses that differ but little from circles.