Vv. Aa. 
Symmes’s Theory of Concentric Spheres 

According to Symmes’s Theory, the earth, as well as all the celestial orbicular bodies existing in the universe, visible and invisible, which partake in any degree of a planetary nature, from the greatest to the smallest, from the sun, down to the most minute blazing meteor or falling star, are all constituted in a greater or less degree, of a collection of spheres, more or less solid, concentric with each other, and more or less open at their poles; each sphere being separated from its adjoining compeers by space replete with aerial fluids; that every portion of infinite space, except what is occupied by spheres, is filled with an aerial elastic fluid, more subtile than common atmospheric air; and constituted of innumerable small concentric spheres, too minute to be visible to the organ of sight assisted by the most perfect microscope, and so elastic that they continually press on each other, and change their relative situations as often as the position of any piece of matter in space may change its position: thus causing a universal pressure, which is weakened by the intervention of other bodies in proportion to the subtended angle of distance and dimension; necessarily causing the body to move towards the points of decreased pressure.