Were we in search of design in nature, or an illustration of the wonders of the microscope, no better example could be suggested to us than the form and structure of a fly. Its tiny body is even more wonderful than the body of a man. Take, for instance, its marvellous power of walking. It can walk anywhere or anyhow, setting every principle of gravitation at defiance by promenading head downwards along the ceiling, or skipping up and down the glittering window-pane, pursuing objects that to us are quite invisible. How is the feat accomplished? What peculiarity has its little foot that the daring acrobat can keep itself suspended in that dizzy and foolhardy position? The microscope gives us the answer. The foot consists of two pads covered with innumerable short hairs, and these hairs are hollow, having trumpet-shaped mouths filled with gum. This gum becomes so hard when exposed to the air, that it will not dissolve in water, so that at every step the fly glues itself to the ceiling, and there it would remain unless it knew how to lift its feet. It lifts them in a slanting direction while the gum is still moist, just as you would remove a moist postage stamp by taking hold of one corner and gently drawing it back. And think of the creature’s eye. It can observe everything in four-fifths of the circle round it, so that to compete with a fly we would require two more pair of eyes, one at the side and another at the back of our head. But in no sense can we compete with these aerial nomads. They have three sets of brain instead of one. They have wings, which we have not. They have six legs instead of two; and their proboscis or trunk is as far beyond that of an elephant "as a railway engine is beyond a wheelbarrow." As seen under a powerful microscope, the structure of a common fly is a perfect marvel of design, and it may well excite our curiosity and call forth our admiration. It points us to the greatness and wisdom of Him whose works are as perfect in the tiniest insect as in the brightest star, whose power is as manifest in the humblest sea-shell as in the huge leviathan that makes the ocean its playground— "All are but parts of one stupendous whole, Whose body Nature is, and God the soul." II.—ITS USEFULNESS. Instead of usefulness, one might almost be tempted to say that the first law of their nature is to _torment_ people; but the service they render to the world at large must not be lightly esteemed.