David Trowbridge

“ It is quite possible for us to guess at the extent and density of their atmospheres, but, unless we subject our guesses to calculation, it cannot be said that they are of much use to us, since the planets are too far from us to allow direct observations to settle any points in dispute. Let us, therefore, assume Jupiter and Saturn to be globes of much higher temperature than the earth's, and that this temperature varies from the surface upward inversely as the square of the distance from the centre of the planet. ”

“ Let us assume the density of the atmosphere at the upper surface of the clouds to be equal to that of our atmosphere at the height of about fifteen miles, and we shall perhaps regard it as sufficiently rare. The height of the upper cloud-layers above the surface proper of the planets will now depend on the surface-temperature and on the mass of the atmosphere. The law of density for different heights above the surface of the planets is almost independent of the mass of the atmosphere, unless we consider the mass as very great in comparison with that of the planet which it surrounds. ”

“ NOT many years ago the planets Jupiter and Saturn were regarded as solid bodies, their small relative density being supposed to be due either to the peculiar arrangement of the materials which compose them, or to the small specific gravity of the materials themselves. ”