The Rainbow is impression gendered in an hollow cloud and dewy, disposed to rain in endless many gutters, as it were shining in a mirror, and is shapen as a bow, and sheweth divers colours, and is gendered by the beams of the sun or of the moon. And is but seldom gendered by beams of the moon, no more but twice in fifty years, as Aristotle saith. In the rainbow by cause of its clearness be seen divers forms, kinds, and shapes that be contrary. Therefore the bow seemeth coloured, for, as Bede saith, it taketh colour of the four elements. For therein, as it were in any mirror, shineth figures and shapes and kinds of elements. For of fire he taketh red colour in the overmost part, and of earth green in the nethermost, and of the air a manner of brown colour, and of water somedeal blue in the middle. And first is red colour, that cometh out of a light beam, that touches the outer part of the roundness of the cloud: then is a middle colour somedeal blue, as the quality asketh, that hath mastery in the vapour, that is in the middle of the cloud. Then the nethermost seemeth a green colour in the nether part of a cloud; there the vapour is more earthly. And these colours are more principal than others. As Beda saith, and the master of stories, forty years tofore the doom, the rainbow shall not be seen, and that shall be token of drying, and of default of elements. And though dew be a manner of airy substance, and most subtle outward, natheless in a wonder manner it is strong in working and virtue. For it besprinkleth the earth, and maketh it plenteous, and maketh flour, pith, and marrow increase in corn and grains: and fatteth and bringeth forth broad oysters and other shell fish in the sea, and namely dew of spring time. For by night in spring time oysters open themselves against dew, and receive dew that cometh in between the two shells, and hold and keep it; and that dew so holden and kept feedeth the flesh, and maketh it fat; and by its incorporation with the inner parts of the fish breedeth a full precious gem, a stone that is called Margarita. Also the birds of ravens, while they are whitish in feathers, ere they are black, dew feedeth and sustaineth them, as Gregory saith. Fumosities that are drawn out of the waters and off the earth by strength of heat of heaven are drawn to the nethermost part of the middle space of the air, and there by coldness of the place they are made thick, and then by heat dissolving and departing the moisture thereof and not wasting all, these fumosities are resolved and fall and turn into rain and showers.