PHYSICAL ASTRONOMY
Has been made the subject of much diligent research and study. Some facts respecting the physical elements and structure of the sun and planets have been ascertained with reasonable certainty, but much is still in doubt. Assuming that the essential properties of matter are the same everywhere, we may tell with assurance of what the sun and stars are made, provided all solar and stellar phenomena are explained by physical laws that are understood, and in operation around us. This has been done in part, but not so as to harmonize the views of all astronomers. Since the use of the spectroscope[5] results have been more satisfactory, and on some questions of much interest, conjecture and theory have given place to certainty. By the decomposition of sunbeams or pencils of solar light, the refracted rays show the presence of several distinct chemical elements. Finding by a qualitative analysis that there is iron, copper, zinc, nickel, sodium, and other terrestrial substances in the solar and stellar spectra, we know that they enter into the composition of those celestial bodies. But in what proportions or combinations they exist is not known.