“But say, what mean those colored streaks in heaven Distended, as the brow of God appeased? Or serve they, as a flowery verge to bind The fluid skirts of that same watery cloud, Lest it again dissolve, and shower the earth? To whom the Archangel: Dexterously thou aim’st; So willingly doth God remit his ire— That he relents, not to blot out mankind; And makes a covenant never to destroy The earth again by flood; nor let the sea Surpass its bounds; nor rain to drown the world, With man therein, or beast; but when he brings O’er the earth a cloud, will therein set His triple-colored bow, whereon to look, And call to mind his covenant.” It is happily remarked by Mr. Prout, in his Bridgewater Treatise, that no pledge could have been more felicitous or satisfactory; for, in order that the rainbow may appear, the clouds must be _partial_, and hence its existence is absolutely incompatible with _universal_ deluge from above. So long, therefore, as “He doth set his bow in the clouds,” so long have we full assurance that these clouds must continue to shower down good, and not evil, to the earth. [Illustration: Rainbow.] When rain is falling, and the sun is on the horizon, the bow appears a complete semicircle, if the rain-cloud is sufficiently extensive to display it. Its extent diminishes as the solar altitude increases, because the colored arch is a portion of a circle whose centre is a point in the sky directly opposite to the sun. Above the height of 45° the primary bow is invisible, and hence, in our climate, the rainbow is not seen in summer about the middle of the day. In peculiar positions a complete circle may be beheld, as when the shower is on a mountain, and the spectator in a valley; or when viewed from the top of a lofty pinnacle, nearly the whole circumference may sometimes be embraced. Ulloa and Bouguer describe circular rainbows, frequently seen on the mountains, which rise above the table-land of Quito. When rain is abundant, there is a secondary bow distinctly seen, produced by a double reflection. This is exterior to the primary one, and the intervening space has been observed to be occupied by an arch of colored light. The secondary bow differs from the other, in exhibiting the same series of colors in an inverted order. Thus the red is the uppermost color in the interior bow, and the violet in the exterior. A tertiary bow may exist, but it is so exceedingly faint from the repeated reflections, as to be scarcely ever perceptible. The same lovely spectacle may be seen when the solar splendor falls upon the spray of the cataract and the waves, the shower of an artificial fountain, and the dew upon the grass. There is hardly any other object of nature more pleasing to the eye, or soothing to the mind, than the rainbow, when distinctly developed—a familiar sight in all regions, but most common in mountainous districts, where the showers are most frequent.