The Practical Astronomer. Thomas Dick

depends on the refraction of light.—It is worthy of particular notice that all the phenomena of optical lenses now described, depend upon that peculiar property which the Creator has impressed upon the rays of light, that, when they are refracted to a focus by a convex transparent substance, they depict an accurate image of the objects whence they proceed. This, however common, and however much overlooked by the bulk of mankind, is indeed a very wonderful property with which light has been endued. Previous to experience we could have had no conception that such an effect would be produced; and, in the first instance, we could not possibly have traced it to all its consequences. All the objects in creation might have been illuminated as they now are, for aught we know, without sending forth either direct or reflected rays with the property of forming exact representations of the objects whence they proceeded. But this we find to be a universal law in regard to light of every description, whether as emanating directly from the sun, or as reflected from the objects he illuminates, or as proceeding from bodies artificially enlightened. It is a law or a property of light not only in our own system, but throughout all the systems of the universe to which mortal eyes have yet penetrated. The rays from the most distant star which astronomers have descried, are endued with this property, otherwise they could never have been perceived by means of our optical instruments; for it is by the pictures or images formed in these instruments that such distant objects are brought to view. Without this property of light, therefore, we should have had no telescopes, and consequently we could not have surveyed, as we can now do, the hills and vales, the deep caverns, the extensive plains, the circular ranges of mountains, and many other novel scenes which diversify the surface of our moon. We should have known nothing of the stupendous spots which appear on the surface of the sun—of the phases of Venus—of the satellites and belts of Jupiter—of the majestic rings of Saturn—of the existence of Uranus and his six moons,—or of the planets Vesta, Juno, Ceres, and Pallas, nor could the exact bulks of any of these bodies have been accurately determined. But, above all, we should have been entirely ignorant of the wonderful phenomena of double stars—which demonstrate that suns revolve around suns—of the thousands and millions of stars which crowd the profundities of the Milky Way and other regions of the heavens—of the thousands of Nebulæ or starry systems which are dispersed throughout the immensity of the firmament, and many other objects of sublimity and grandeur, which fill the contemplative mind with admiration and awe, and raise its faculties to higher conceptions than it could otherwise have formed of the omnipotence and grandeur of the Almighty Creator.

      Without this property of the rays of light we should likewise have wanted the use of the microscope—an instrument which has disclosed a world invisible to common eyes, and has opened to our view the most astonishing exhibitions of Divine mechanism, and of the wisdom and intelligence of the Eternal Mind. We should have been ignorant of those tribes of living beings, invisible to the unassisted eye, which are found in water, vinegar, and many other fluids—many of which are twenty thousand times smaller than the least visible point, and yet display the same admirable skill and contrivance in their construction, as are manifested in the formation of the larger animals. We should never have beheld the purple tide of life, and even the globules of the blood rolling with swiftness through veins and arteries smaller than the finest hair; or had the least conception that numberless species of animated beings, so minute that a million of them are less than a grain of sand, could have been rendered visible to human eyes, or that such a number of vessels, fluids, movements, diversified organs of sensation, and such a profusion of the richest ornaments and the gayest colours could have been concentrated in a single point. We should never have conceived that even the atmosphere is replenished with invisible animation, that the waters abound with countless myriads of sensitive existence, that the whole earth is full of life, and that there is scarcely a tree, plant, or flower, but affords food and shelter to a species of inhabitants peculiar to itself, which enjoy the pleasures of existence and share in the bounty of the Creator. We could have formed no conception of the beauties and the varieties of mechanism which are displayed in the scenery of that invisible world to which the microscope introduces us—beauties and varieties, in point of ornament and delicate contrivance, which even surpass what is beheld in the visible operations and aspect of nature around us. We find joints, muscles, a heart, stomach, entrails, veins, arteries, a variety of motions, a diversity of forms, and a multiplicity of parts and functions—in breathing atoms. We behold in a small fibre of a peacock’s feather, not more than one-eighth of an inch in length, a profusion of beauties no less admirable than is presented by the whole feather to the naked eye—a stem sending out multitudes of lateral branches, each of which emits numbers of little sprigs, which consist of a multitude of bright shining globular parts, adorned with a rich variety of colours. In the sections of plants, we see thousands and ten thousands of tubes and pores, and other vessels for the conveyance of air and juices for the sustenance of the plant; in some instances, more than ten hundred thousand of these being compressed within the space of a quarter of an inch in diameter, and presenting to the eye the most beautiful configurations. There is not a weed, nor a moss, nor the most insignificant vegetable, which does not show a multiplicity of vessels disposed in the most curious manner for the circulation of sap for its nourishment, and which is not adorned with innumerable graces for its embellishment. All these and ten thousands of other wonders which lie beyond the limits of natural vision, in this new and unexplored region of the universe, would have been for ever concealed from our view, had not the Creator endued the rays of light with the power of depicting the images of objects, when refracted by convex transparent substances.

      In this instance, as well as in many others, we behold a specimen of the admirable and diversified effects, which the Creator can produce from the agency of a single principle in nature. By means of optical instruments, we are now enabled to take a more minute and expansive view of the amazing operations of nature, both in heaven and on earth, than former generations could have surmised. These views tend to raise our conceptions of the attributes of that Almighty Being, who presides over all the arrangements of the material system, and to present them to our contemplation in a new, a more elevated, and expansive point of view. There is, therefore, a connection which may be traced between the apparently accidental principle of the rays of light forming images of objects, and the comprehensive views we are now enabled to take of the character and perfections of the Divinity. Without the existence of the law or principle alluded to, we could not, in the present state, have formed precisely the same conceptions either of the Omnipotence, or of the wisdom and intelligence of the Almighty. Had no microscope ever been invented, the idea never could have entered into the mind of man, that worlds of living beings exist beyond the range of natural vision, that organized beings possessed of animation exist, whose whole bulk is less than the ten hundred thousandth part of the smallest grain of sand; that, descending from a visible point to thousands of degrees beyond it, an invisible world exists, peopled with tribes of every form and size, the extent of which, and how far it verges towards infinity downwards, mortals have never yet explored, and perhaps will never be able to comprehend. This circumstance alone presents before us the perfections of the divinity in a new aspect, and plainly intimates that it is the will and the intention of the Deity, that we should explore his works, and investigate the laws by which the material world is regulated, that we may acquire more expansive views of his character and operations. The inventions of man in relation to art and science, are not therefore to be considered as mere accidental occurrences, but as special arrangements in the divine government, for the purpose of carrying forward the human mind to more clear and ample views of the scenes of the universe, and of the attributes and the agency of Him “who is wonderful in counsel and excellent in working.”

CHAPTER IV.

       Table of Contents

      ON THE REFLECTION OF LIGHT.

      The reflection of the rays of light is that property by which—after approaching the surfaces of bodies, they are thrown back, or repelled. It is in consequence of this property that all the objects around us, and all the diversified landscapes on our globe, are rendered visible. It is by light reflected from their surfaces that we perceive the planetary bodies and their satellites, the belts of Jupiter, the rings of Saturn, the various objects which diversify