[_Her hardening srata spread_. l. 35. The granite, or moor-stone, or porphory, constitute the oldest part of the globe, since the limestone, shells, coralloids, and other sea-productions rest upon them; and upon these sea-productions are found clay, iron, coal, salt, and siliceous sand or grit-stone. Thus there seem to be three divisions of the globe distinctly marked; the first I suppose to have been the original nucleus of the earth, or lava projected from the sun; 2. over this lie the recrements of animal and vegetable matter produced in the ocean; and, 3. over these the recrements of animal and vegetable matter produced upon the land. Besides these there are bodies which owe their origin to a combination of those already mentioned, as siliceous sand, fluor, alabaster; which seem to have derived their acids originally from the vegetable kingdom, and their earthy bases from sea-productions. See additional notes, No. XVI. on calcareous earth.] [_Raised her primeval islands_. l. 36. The nucleus of the earth, still covered with water, received perpetual increase by the immense quantities of shells and coralloids either annually produced and relinquishied, or left after the death of the animals. These would gradually by their different degrees of cohesion be some of them more and others less removable by the influence of solar tides, and gentle tropical breezes, which then must have probably extended from one pole to the other; for it is supposed the moon was not yet produced, and that no storms or unequal winds had yet existence. Hence then the primeval islands had their gradual origin, were raised but a few feet above the level of the sea, and were not exposed to the great or sudden variations of heat and cold, as is so well explained in Mr. Whitehurst's Theory of the Earth, chap. xvi. Whence the paradise of the sacred writers, and the golden age of the profane ones, seems to have had a real existence. As there can be no rainbow, when the heavens are covered with clouds, because the sun-beams are then precluded from falling upon the rain-drops opposite to the eye of the spectator, the rainbow is a mark of gentle or partial showers. Mr. Whitehurst has endeavoured to show that the primitive islands were only moistened by nocturnal dews and not by showers, as occurs at this day to the Delta of Egypt; and is thence of opinion, that the rainbow had no existence till after the production of mountains and continents. As the salt of the sea has been gradually accumulating, being washed down into it from the recrements of animal and vegetable bodies, the sea must originally have been as fresh as river water; and as it is not yet saturated with salt, must become annually more saline. See note on l. 119 of this Canto.]