The exploring party next passes through Narrow Cañon, nine and a half miles long, Glen Cañon, one hundred and forty-nine miles in length; and Marble Cañon, sixty-five and one-half miles long. The depth of the last named is three thousand five hundred feet at the lower end. They emerge from Marble Cañon August 10, and find themselves separated from the Grand Cañon of the Colorado, the "Great Unknown," by the narrow valley of the Little Colorado. The Grand Cañon is now entered and safely passed, a distance of two hundred and seventeen and one-half miles, terminating with the Grand Wash. We are compelled to terminate this article abruptly for lack of space. It is proper to say that this journey has scarcely ever been equaled for daring and hardihood. Each time they descended a rapids, they were liable to come to a fall too great to shoot over, with walls so steep they could not be climbed, and rapids so swift as to prevent return. The Grand Cañon, as one of the wonders of the world, is visited every summer by hundreds of tourists. OPTIMUS. BY REV. CHARLES COKE WOODS. A glow-worm in the grass at night shed forth Its feeble light, but darkness deepened fast; The wee thing did its uttermost to banish night, And that, forsooth, was truest toil, indeed, Success in God's clear sight, though in man's view, Obscured by things of sense, 'twas but defeat. A fire-fly flashed its fitful light, while soft The evening shadows fell, and clouds hid stars, And veiled in black the gentle moon's bright face; As if the night, like one afraid, would haste To flee when lightning flashed from those small wings, With courage high the insect gave its light, Though all alone with none to proffer aid-- Nor sun, nor moon, nor star a single beam. At last the dawn shot crimson up the sky; The tiny toilers crawled away to rest, And sweet, methinks, was their well-earned repose, For each its place had filled, its task had done In keeping with the great Creator's thought. HOW THE EARTH WAS FORMED. T. C. CHAMBERLIN, Head Professor of Geology, University of Chicago. Just how the earth was formed at the outset is not certainly known. The most common view of men of science is that it was once in the form of a fiery gas. It is supposed that all the planets and satellites that now revolve around the sun were once a part of a common mass of gas in the form of a vast sphere which was very large and very hot. This gradually lost its heat and shrank as most bodies do when they cool. If it was not already whirling round at the outset it must have come to do so as it shrank, and as more and more of its heat was lost it rotated more and more rapidly. At length it came to whirl so fast that the outer part, which was moving fastest, could no longer be held down to the surface, and so it separated in the form of a ring around the equator of the great sphere.