figure 35.
figure 35.
It appears, then, that the first or primary bow is formed by two refractions and one reflection; but there is frequently a second bow, on the outside of the other, which is considerably fainter. This is produced by drops of rain above the drop we have supposed at A. If B (fig. 35.) represent one of these drops, the ray to be sent to the eye enters the drop near the bottom, and sufferstwo refractionsandtwo reflections, by which means the colours become reversed, that is, the violet is lowest in theexteriorbow, and the red is lowest in theinteriorone, and the other colours are reversed accordingly. The ray T is refracted atR: a part of it is reflected fromStoT, and atTit suffers another reflection fromTtoU. At the pointsSandTpart of the raypasses throughthe drop on account of its transparency, towardsWandX, and therefore we say thatpartonly of the ray is reflected. By these losses and reflections the exterior bow becomes faint and ill-defined in comparison of the interior or primary bow. In this case the upper part of the secondary bow will not be seen when the sun is above 54° 10´ above the horizon; and the lower part of the bow will not be seen when the sun is 60° 58´ above the horizon.
figure 36.
figure 36.
For the further illustrations of this subject, we may introduce the following section of a bow, (fig. 36.) and, in order to prevent confusion in attempting to represent all the different colours—let us suppose only three drops of rain, and three different colours, as shown in the figure. The spectator O being in the centre of the two bows, here represented,—the planes of which must be considered as perpendicular to his view—the drops A,B, and C produce part of the interior bow by two refractions and one reflection as stated above,and the drops D,E,F will produce the exterior bow by two refractions and two reflections, the sun’s rays being represented by 3,3. It is evident that the angle COP is less than the angle BOP, and that the angle AOP is the greatest of the three. The largest angle, then, is formed by the red rays, the middle one consists of the green, and the smallest the purple or violet. All the drops of rain, therefore, that happen to be in a certain position with respect to the spectator’s eye, will reflect the red rays, and form a band or semicircle of red, and so of the other colours from drops in other positions. If the spectator alters his station, he will see a bow, but not the same as before; and if there be many spectators, they will each see a different bow, though it appears to be the same.
The rainbow assumes asemicircularappearance, because it is only at certain angles that the refracted rays are visible to our eyes, as is evident from the experiment of the glass globe formerly alluded to, which will refract the rays only in a certain position. We have already stated that the red rays make an angle of 42° 2´, and the violet an angle of 40° 17´. Now, if a line be drawn horizontally from the spectator’s eye, it is evident that angles formed with this line, of a certain dimension, in every direction, will produce a circle, as will appear by attaching a cord of a given length to a certain point, round which it may turn as round its axis; and, in every point will describe an angle with the horizontal line of a certain and determinate extent.
Sometimes it happens thatthreeor more bows are visible, though with different degrees of distinctness. I have more than once observed this phenomenon, particularly in Edinburgh, in the month of August, 1825, when three rainbowswere distinctly seen in the same quarter of the sky; and, if I recollect right, a fragment of a fourth made its appearance. This happens when the rays suffer a third or fourth reflection; but, on account of the light lost by so many reflections, such bows are, for the most part, altogether imperceptible.
If there were no ground to intercept the rain and the view of the observer, the rainbow would form acomplete circle, the centre of which is diametrically opposite to the sun. Such circles are sometimes seen in the spray of the sea or of a cascade, or from the tops of lofty mountains, when the showers happen in the vales below. Rainbows of various descriptions are frequently observed rising amidst the spray and exhalations of waterfalls, and among the waves of the sea whose tops are blown by the wind into small drops. There is one regularly seen, when the sun is shining, and the spectator in a proper position, at the fall of Staubbach, in the bosom of the Alps; one near Schaffhausen; one at the cascade of Lauffen; and one at the cataract of Niagara in North America. A still more beautiful one is said to be seen at Terni, where the whole current of the river Velino, rushing from a steep precipice of nearly 200 feet high, presents to the spectator below, a variegated circle, over-arching the fall, and two other bows suddenly reflected on the right and left. Don Ulloa, in the account of his journeys in South America, relates that circular rainbows are frequently seen on the mountains above Quito in Peru. It is said that a rainbow was once seen near London, caused by the exhalations of that city, after the sun had been below the horizon more than twenty minutes.14A navalfriend, says Mr. Bucke, informed me, that, as he was one day watching the sun’s effect upon the exhalations near Juan Fernandez, he saw upwards of five-and-twentyires marinæanimate the sea at the same time. In these marine bows the concave sides were turned upwards, the drops of water rising from below, and not falling from above, as in the instances of the aerial arches. Rainbows are also occasionally seen on the grass, in the morning dew, and likewise when the hoar-frost is descending. Dr. Langwith once saw a bow lying on the ground, the colours of which were almost as lively as those of a common rainbow. It was not round but oblong, and was extended several hundred yards. The colours took up less space, and were much more lively in those parts of the bow which were near him than in those which were at a distance. When M. Labillardiere was on Mount Teneriffe, he saw the contours of his body traced on the clouds beneath him in all the colours of the solar bow. He had previously witnessed this phenomenon on the Kesrouan in Asia Minor. The rainbows of Greenland are said to be frequently of a pale white, fringed with a brownish yellow, arising from the rays of the sun being reflected from a frozen cloud.
The following is a summary view of the principal facts which have been ascertained respecting the rainbow:—1. The rainbow can only be seen when it rains, and in that point of the heavens which is opposite to the sun. 2. Both the primary and secondary bows are variegated with all the prismatic colours—the red being the highest colour in the primary, or brightest bow, and the violet the highest in the exterior. 3. The primary rainbow can never be a greater arc than a semicircle;and when the sun is set, no bow, in ordinary circumstances, can be seen. 4. The breadth of the inner or primary bow—supposing the sun but a point—is 1° 45´; and the breadth of the exterior bow 3° 12´, which is nearly twice as great as that of the other; and the distance between the bows is 8° 55´. But since the body of the sun subtends an angle of about half a degree, by so much will each bow be increased, and their distance diminished; and therefore the breadth of the interior bow will be 2° 15´, and that of the exterior, 3° 42´, and their distance 8° 25´. The greatest semidiameter of the interior bow, on the same grounds, will be 42° 17´, and the least of the exterior bow 50° 43´. 5. When the sun is in the horizon, either in the morning or evening, the bows will appear complete semicircles. On the other hand, when the sun’s altitude is equal to 42° 2´ or to 54° 10´, the summits of the bows will be depressed below the horizon. Hence, during the days of summer, within a certain interval each day, no visible rainbows can be formed, on account of the sun’s high altitude above the horizon. 6. The altitude of the bows above the horizon, or surface of the earth, varies, according to the elevation of the sun. The altitude, at any time, may be taken by a common quadrant, or other angular instrument; but, if the sun’s altitude at any particular time be known, the height of the summit of any of the bows may be found, by subtracting the sun’s altitude from 42° 2´ for the inner bow, and from 54° 10´, for the outer. Thus, if the sun’s altitude were 26°, the height of the primary bow would 16° 2´, and of the secondary, 28° 10´. It follows, that the height and the size of the bows diminish as the altitude of the sun increases. 7. If the sun’s altitude is morethan 42 degrees, and less than 54°, the exterior bow may be seen though the interior bow is invisible. 8. Sometimes only a portion of an arch will be visible while all the other parts of the bow are invisible. This happens when the rain does not occupy a space of sufficient extent to complete the bow; and the appearance of this position, and even of the bow itself, will be various, according to the nature of the situation, and the space occupied by the rain.
The appearance of the rainbow may be produced by artificial means, at any time when the sun is shining and not too highly elevated above the horizon. This is effected by means of artificial fountains orJet d’eaus, which are intended to throw up streams of water to a great height. These streams, when they spread very wide, and blend together in their upper parts, form, when falling, a shower of artificial rain. If, then, when the fountain is playing, we move between it and the sun, at a proper distance from the fountain, till our shadow point directly towards it, and look at the shower,—we shall observe the colours of the rainbow, strong and vivid; and, what is particularly worthy of notice, the bow appears, notwithstanding the nearness of the shower, to be as large, and as far off, as the rainbow which we see in a natural shower of rain. The same experiment may be made by candle-light, and with any instrument that will form an artificial shower.
Lunar Rainbows.—A lunar bow is sometimes formed at night by the rays of the moon striking on a rain-cloud, especially when she is about the full. But such a phenomenon is very rare. Aristotle is said to have considered himself the first who had seen a lunar rainbow. For more than a hundred years prior to the middle of the last century,we find only two or three instances recorded in which such phenomena are described with accuracy. In the philosophical transactions for 1783, however, we have an account of three having been seen in one year, and all in the same place, but they are by no means common phenomena. I have had an opportunity within the last twenty years of witnessing two phenomena of this description—one of which was seen at Perth, on a sabbath evening, in the autumn of 1825, and the other at Edinburgh, on Wednesday, the 9th of September 1840, about eight o’clock in the evening—of both which I gave a detailed description in some of the public journals. The Moon, in both cases, was within a day or two of the full; the arches were seen in the northern quarter of the heavens, and extended nearly from east to west, the moon being not far from the southern meridian. The bows appeared distinct and well defined, but no distinct traces of the prismatic colours could be perceived on any of them. That which appeared in 1825 was the most distinctly formed, and continued visible for more than an hour. The other was much fainter, and lasted little more than half an hour, dark clouds having obscured the face of the moon. These bows bore a certain resemblance to some of the luminous arches which sometimes accompany the Aurora Borealis, and this latter phenomenon has not unfrequently been mistaken for a Lunar rainbow; but they may be always distinguished by attending to the phases and position of the moon. If the moon be not visible above the horizon, if she be in her first or last quarter, or if any observed phenomenon be not in a direction opposite to the moon, we may conclude with certainty that, whatever appearance is presented, there is no lunar rainbow.
The rainbow is an object which has engaged universal attention, and its beautiful colours and form have excited universal admiration. The poets have embellished their writings with many beautiful allusions to this splendid meteor; and the playful school-boy, while viewing the ‘bright enchantment,’ has frequently run ‘to catch the falling glory.’ When its arch rests on the opposite sides of a narrow valley, or on the summits of two adjacent mountains, its appearance is both beautiful and grand. In all probability, its figure first suggested the idea ofarches, which are now found of so much utility in forming aqueducts and bridges, and for adorning the architecture of palaces and temples. It is scarcely possible seriously to contemplate this splendid phenomenon, without feeling admiration and gratitude towards that wise and beneficent Being, whose hands have bent it into so graceful and majestic a form, and decked it with all the pride of colours. “Look upon the rainbow,” says the son of Sirach,15and praise Him that made it: very beautiful it is in the brightness thereof. It compasseth the heaven about with a glorious circle, and the hands of the Most High have bended it." To this grand etherial bow, the inspired writers frequently allude as one of the emblems of the majesty and splendour of the Almighty. In the prophecies of Ezekiel, the throne of Deity is represented as adorned with a brightness “like the appearance of the bow that is in the cloud in the day of rain—the appearance of the likeness of the glory of Jehovah.” And, in the visions recorded in the Book of the Revelations, where the Most High is represented as sitting upon a throne; “there was a rainbow round about the throne, in sight likeunto an emerald,” as an emblem of his propitious character and of his faithfulness and mercy. After the deluge, this bow was appointed as a sign and memorial of the covenant which God made with Noah and his sons, that a flood of waters should never again be permitted to deluge the earth and its inhabitants;—and as a pledge of inviolable fidelity and Divine benignity. When, therefore, we at any time behold “the bow in the cloud,” we have not only a beautiful and sublime phenomenon presented to the eye of sense, but also a memorial exhibited to the mental eye, assuring us, that, “While the earth remaineth, seed-time and harvest, and cold and heat, and summer and winter, and day and night,shall not cease.”16
——On the broad sky is seen“A dewy cloud, and in the cloud a bowConspicuous, with seven listed colours gayBetokening peace with God and covenant new.—He gives a promise never to destroyThe earth again by flood, nor let the seaSurpass his bounds, nor rain to drown the world.”Milton. Par. Lost, Book XI.
——On the broad sky is seen“A dewy cloud, and in the cloud a bowConspicuous, with seven listed colours gayBetokening peace with God and covenant new.—He gives a promise never to destroyThe earth again by flood, nor let the seaSurpass his bounds, nor rain to drown the world.”Milton. Par. Lost, Book XI.
——On the broad sky is seen“A dewy cloud, and in the cloud a bowConspicuous, with seven listed colours gayBetokening peace with God and covenant new.—He gives a promise never to destroyThe earth again by flood, nor let the seaSurpass his bounds, nor rain to drown the world.”Milton. Par. Lost, Book XI.
Colour is one of the properties of light which constitutes, chiefly, the beauty and sublimity of the universe. It is colour, in all its diversified shades, which presents to our view that almost infinite variety of aspect which appears on the scene of nature, which gives delight to the eye and the imagination, and which adds a fresh pleasure to every new landscape we behold. Every flower which decks our fields and gardens is compounded of different hues; every plain is covered with shrubs and trees of different degrees of verdure; and almost every mountain is clothed with herbs and grass of different shade from those which appear on the hills and landscape with which it is surrounded. In the country, during summer, nature is every day, and almost every hour, varying her appearance, by the multitude and variety of her hues and decorations, so that the eye wanders with pleasure over objects continually diversified, and extending as far as the sight can reach. In the flowers with which every landscape is adorned, what a lovely assemblage of colours, and what a wonderful art in the disposition of their shades! Here, a light pencil seems to have laid on the delicate tints; there, they are blended according to the nicest rules of art. Although green is the general colour which prevails over the scene of sublunary nature, yet it is diversified by a thousand different shades, so that every species of tree,shrub and herb, is clothed with its own peculiar verdure. The dark green of the forests is thus easily distinguished from the lighter shades of cornfields and the verdure of the lawns. The system of animated nature likewise, displays a diversified assemblage of beautiful colours. The plumage of birds, the brilliant feathers of the peacock, the ruby and emerald hues which adorn the little humming-bird, and the various embellishments of many species of the insect tribe, present to the eye, in every region of the globe, a scene of diversified beauty and embellishment. Nor is the mineral kingdom destitute of such embellishments. For some of the darkest and most unshapely stones and pebbles, when polished by the hand of art, display a mixture of the most delicate and variegated colours. All which beauties and varieties in the scene around us are entirely owing to that property, in every ray of light, by which it is capable of being separated into the primitive colours.
To the same cause, likewise, are to be ascribed those beautiful and diversified appearances, which frequently adorn the face of the sky,—the yellow, orange and ruby hues which embellish the firmament at the rising of the sun, and when he is about to descend below the western horizon; and those aerial landscapes, so frequently beheld in tropical climes, where rivers, castles and mountains, are depicted rolling over each other along the circle of the horizon. The clouds, especially in some countries, reflect almost every colour in nature. Sometimes they wear the modest blush of the rose; sometimes they appear like stripes of deep vermillion, and sometimes as large brilliant masses tinged with various hues; now they are white as ivory, and now as yellow as native gold. In sometropical countries, according to St. Pierre, the clouds roll themselves up into enormous masses as white as snow, and are piled upon each other, like the Cordeliers of Peru, and are moulded into the shape of mountains, of caverns and of rocks. When the sun sets behind this magnificent aërial net-work, a multitude of luminous rays are transmitted through each particular interstice, which produce such an effect, that the two sides of the lozenge illuminated by them, have the appearance of being begirt with a fillet of gold; and the other two which are in the shade, seem tinged with a superb ruddy orange. Four or five divergent streams of light, emanating from the setting sun up to the zenith, clothe with fringes of gold the undeterminate summits of this celestial barrier, and proceed to strike with the reflexes of their fires the pyramids of the collateral aerial mountains, which then appear to consist of silver and vermilion.—In short, colour diversifies every sublunary scene, whether on the earth or in the atmosphere, it imparts a beauty to the phenomena of falling stars, of luminous arches, and the coruscations of the Aurora Borealis, and gives a splendour and sublimity to the spacious vault of heaven.
Let us now consider for a moment, what would be the aspect of nature, if, instead of the beautiful variety of embellishments which now appear on every landscape, and on the concave of the sky,—oneuniform colour had been thrown over the scenery of the universe. Let us conceive the whole of terrestrial nature to be covered with snow, so that not an object on earth should appear with any other hue, and that the vast expanse of the firmament presented precisely the same uniform aspect. What would be the consequence? The light of the sun would be strongly reflectedfrom all the objects within the bounds of our horizon, and would produce a lustre which would dazzle every eye. The day would acquire a greaterbrightnessthan it now exhibits, and our eyes might, after some time, be enabled freely to expatiate over the surrounding landscape; but every thing, though enlightened, would appearconfused, and particular objects would scarcely be distinguishable. A tree, a house or a church, near at hand, might possibly be distinguished, on account of its elevation above the general surface of the ground, and the bed of a river by reason of its being depressed below it. But we should be obliged rather to guess, and to form a conjecture as to the particular object we wished to distinguish, than to arrive at any certain conclusion respecting it; and if it lay at a considerable distance, it would be impossible, with any degree of probability, to discriminate any one object from another. Notwithstanding the universal brightness of the scene, the uniformity of colour thrown on every object, would most certainly prevent us from distinguishing a church from a palace, a cottage from a knoll or a heap of rubbish, a splendid mansion from rugged rocks, the trees from the hills on which they grow, or a barren desert from rich and fertile plains. In such a case, human beings would be confounded, and even friends and neighbours be at a loss to recognize one another.
The vault of heaven, too, would wear a uniform aspect. Neither planets nor comets would be visible to any eye, nor those millions of stars which now shine forth with so much brilliancy, and diversify the nocturnal sky. For, it is by the contrast produced by the deep azure of the heavens and the white radiance of the stars, that those bodies are rendered visible. Were they depictedon a pure white ground, they would not be distinguished from that ground, and would consequently be invisible, unless any of them occasionally assumed a different colour. Of course, all that beautiful variety of aspect which now appears on the face of sublunary nature—the rich verdure of the fields, the stately port of the forest, the rivers meandering through the valleys, the splendid hues that diversify and adorn our gardens and meadows, the gay colouring of the morning and evening clouds, and all that variety which distinguishes the different seasons, would entirely disappear. As every landscape would exhibit nearly the same aspect, there would be no inducement to the poet and the philosopher to visit distant countries to investigate the scenes of nature, and journeyings from one region to another would scarcely be productive of enjoyment. Were any other single colour to prevail, nearly the same results would ensue. Were a deep ruddy hue to be uniformly spread over the scene of creation, it would not only be offensive to the eye, but would likewise prevent all distinction of objects. Were a dark blue or a deep violet to prevail, it would produce a similar effect, and at the same time, present the scene of nature as covered with a dismal gloom. Even if creation were arrayed in a robe ofgreen, which is a more pleasant colour to the eye—were it not diversified with the different shades it now exhibits, every object would be equally undistinguishable.
Such would have been the aspect of creation, and the inconveniences to which we should have been subjected, had the Creator afforded us light without that intermixture of colours which now appears over all nature, and which serves to discriminate one object from another. Even ourvery apartments would have been tame and insipid, incapable of the least degree of ornament, and the articles with which they are furnished, almost undistinguishable, so that in discriminating one object from another, we should have been as much indebted to the sense of touch as to the sense of vision. Our friends and fellow men would have presented no objects of interest in our daily associations. The sparkling eye, the benignant smile, the modest blush, the blended hues of white and vermillion in the human face, and the beauty of the female countenance, would all have vanished, and we should have appeared to one another as so many moving marble statues cast nearly in the same mould. But, what would have been worst of all, the numerous delays, uncertainties and perplexities to which we should have been subjected, had we been under the necessity, every moment, of distinguishing objects by trains of reasoning, and by circumstances of time, place, and relative position? An artist, when commencing his work in the morning, with a hundred tools of nearly the same size and shape around him, would have spent a considerable portion of his time before he could have selected those proper for his purpose, or the objects to which they were to be applied; and in every department of society, and in all our excursions from one place to another, similar difficulties and perplexities would have occurred. The one half of our time must thus have been employed in uncertain guesses, and perplexing reasonings, respecting the real nature and individuality of objects, rather than in a regular train of thinking and of employment; and after all our perplexities and conjectures, we must have remained in the utmost uncertainty, as to the thousands of scenes and objects, which are now obvious to us, throughthe instrumentality of colours, as soon as we open our eyes.
In short, without colour, we could have had no books nor writings: we could neither have corresponded with our friends by letters, nor have known any thing with certainty, of the events which happened in former ages. No written revelation of the will of God, and of his character, such as we now enjoy, could have been handed down to us from remote periods and generations. The discoveries of science, and the improvements of art, would have remained unrecorded. Universal ignorance would have prevailed throughout the world, and the human mind have remained in a state of demoralization and debasement. All these, and many other inconveniences and evils would have inevitably followed, had not God painted the rays of light with a diversity of colours, And hence we may learn, that the most important scenes and events in the universe, may depend upon the existence of a single principle in nature, and even upon the most minute circumstances, which we may be apt to overlook, in the arrangements of the material world.
In the existing state of things in the visible creation, we cannot but admire the Wisdom and Beneficence of the Deity, in thus enabling us to distinguish objects by so easy and expeditious a mode asthat of colour, which in a moment, discriminates every object and its several relations. We rise in the morning to our respective employments, and our food, our drink, our tools, our books, and whatever is requisite for our comfort, are at once discriminated. Without the least hesitation or uncertainty, and without any perplexing process of reasoning, we can lay our hands on whatever articles we require. Colour clothes every objectwith its peculiar livery, and infallibly directs the hand in its movements, and the eye in its surveys and contemplations. But, this is not the only end which the Divine Being had in view, in impressing on the rays of light a diversity of colours. It is evident, that he likewise intended to minister to ourpleasures, as well as to our wants. To every man of taste, and almost to every human being, the combination of colours in flowers, the delicate tints with which they are painted, the diversified shades of green with which the hills and dales, the mountains and the vales are arrayed; and that beautiful variety which appears in a bright summer day, on all the objects of this lower creation—are sources of the purest enjoyment and delight. It is colour, too, as well as magnitude, that adds to thesublimityof objects. Were the canopy of heaven of one uniform hue, it would fail in producing those lofty conceptions, and those delightful and transporting emotions, which a contemplation of its august scenery is calculated to inspire. Colours are likewise of considerable utility in the intercourse of general society. They serve both for ornaments, and for distinguishing the different ranks and conditions of the community: they add to the beauty and gracefulness of our furniture and clothing. At a glance, they enable us at once to distinguish the noble from the ignoble, the prince from his subjects, the master from his servant, and the widow clothed with sable weeds from the bride adorned with her nuptial ornaments.
Since colours, then, are of so much value and importance, they may be reckoned as holding a rank among the noblest natural gifts of the Creator. As they are of such essential service to the inhabitants of our globe, there can be no doubt that they serve similar or analogous purposesthroughout all the worlds in the universe. The colours displayed in the solar beams are common to all the globes which compose the planetary system, and must necessarily be reflected, in all their diversified hues, from objects on their surfaces. The light which radiates from the fixed stars displays a similar diversity of colours. Some of the double stars are found to emit light of different hues;—the larger star exhibiting light of a ruddy or orange hue, and the smaller one a radiance which approaches to blue or green. There is therefore reason to conclude, that the objects connected with the planets which revolve round such stars—being occasionally enlightened by suns of different hues—will display a more variegated and splendid scenery of colouring than is ever beheld in the world on which we dwell; and that one of the distinguishing characteristics of different worlds, in regard to their embellishments, may consist in the splendour and variety of colours with which the objects on their surfaces are adorned. In the metaphorical description of the glories of the New Jerusalem, recorded in the Book of Revelation, one of the chief characteristics of that city is said to consist in the splendour and diversity of hues with which it is adorned. It is represented as “coming down from heaven,prepared as a bride adorned for her husband,” and as reflecting all the beautiful and variegated colours which the finest gems on earth can exhibit; evidently indicating, that splendour and variety of colouring are some of the grandest features of celestial scenery.
On the whole, the subject of colours, when seriously considered, is calculated to excite us to the adoration of the goodness and intelligence of that Almighty Being whose wisdom planned allthe arrangements of the universe, and to inspire us with gratitude for the numerous conveniences and pleasures we derive from those properties and laws he has impressed on the material system. He might have afforded us light, and even splendid illumination, without the pleasures and advantages which diversified colours now produce, and man and other animated beings might have existed in such a state. But, what a very different scene would the world have presented from what it now exhibits! Of how many thousands of pleasures should we have been deprived! and to what numerous inconveniences and perplexities should we have been subjected! The sublimity and glories of the firmament, and the endless beauties and varieties which now embellish our terrestrial system, would have been for ever unknown, and man could have had little or no incitement to study and investigate the works of his Creator. In this, as well as in many other arrangements in nature, we have a sensible proof of the presence and agency of that Almighty Intelligence “in whom we live, and move, and have our being.” None but an infinitely Wise and Beneficent Being, intimately present in all places, could thus so regularly create in us by means of colour, those exquisite sensations which afford so much delight, and which unite us, as it were, with every thing around us. In the diversity of hues spread over the face of creation, we have as real a display of the Divine presence as Moses enjoyed at the burning bush. The only difference is, that the one was out of the common order of Divine procedure, and the other in accordance with those permanent laws which regulate the economy of the universe. In every colour, then, which we contemplate, we have a sensible memorial of the presence of thatBeing “whose Spirit garnished the heavens and laid the foundations of the earth,” and whose “merciful visitation” sustains us every moment in existence. But the revelation of God to our senses, through the various objects of the material world, has become so familiar, that we are apt to forget the Author of all our enjoyments, even at the moment when we are investigating his works and participating of his benefits. “O that men would praise Jehovah for his goodness, and for his wonderful works towards the children of men.”
The telescope is an optical instrument for viewing objects at a distance. Its name is compounded of two Greek words,—τηλε, which signifies,at a distance, orfar off, and σχοπειν,to view, or tocontemplate. By means of telescopes, remote objects are represented as if they were near, small apparent magnitudes are enlarged, confused objects are rendered distinct, and the invisible and obscure parts of very distant scenes are rendered perceptible and clear to the organ of vision. The telescope is justly considered as a grand and noble instrument. It is not a little surprising that it should be in the power of man to invent and construct an instrument by which objects, too remote for the unassisted eye to distinguish, should be brought within the range of distinctvision, as if they were only a few yards from our eye, and that thousands of august objects in the heavens, which had been concealed from mortals for numerous ages, should be brought within the limits of our contemplation, and be as distinctly perceived, as if we had been transported many millions of miles from the space we occupy, through the celestial regions. The celebrated Huygens remarks, in reference to this instrument, that, in his opinion, ‘the wit and industry of man has not produced any thing so noble and so worthy of his faculties as this sort of knowledge; (namely of the telescope) insomuch that if any particular person had been so diligent and sagacious as to invent this instrument from the principles of nature and geometry,—for my part, I should have thought his abilities were more than human; but the case is so far from this, that the most learned men have not yet been able sufficiently to explain the reason of the effects of this casual invention.’
The persons who constructed the first telescopes, and the exact period when they were first invented, are involved in some degree of obscurity. It does not certainly appear that such instruments were known to the ancients, although we ought not to be perfectly decisive on this point. The cabinets of the curious contain some very ancient gems, of admirable workmanship, the figures on which are so small, that they appear beautiful through a magnifying glass, but altogether confused and indistinct to the naked eye: and, therefore, it may be asked, if they cannot beviewed, how could theybe wrought, without the assistance of glasses? And as some of the ancients have declared that the moon has a form like that of the earth, and has plains, hills, and valleys in it,—how could they know this—unless by mere conjecture,without the use of a telescope? And how could they have known that theMilky Wayis formed by the combined rays of an infinite number of stars? For Ovid states, in reference to this zone, ‘its ground-work is of stars.’ But whatever knowledge the ancients may have possessed of the telescope or other optical glasses, it is quite evident that they never had telescopes of such size and power as those which we now possess; and that no discoveries in the heavens, such as are now brought to light, were made by any of the ancient astronomers; otherwise some allusions to them must have been found in their writings.
Among the moderns, the illustrious Friar Bacon appears to have acquired some rude ideas respecting the construction of telescopes. ‘Lenses and specula’ says he, ‘may be so figured that one object may be multiplied into many, that those which are situated at a great distance may be made to appear very near, that those which are small may be made to appear very large, and those which are obscure very plain; and we can make stars to appear wherever we will.’ From these expressions, it appears highly probable, that this philosopher was acquainted with the general principle both of telescopes and microscopes, and that he may have constructed telescopes of small magnifying power, for his own observation and amusement, although they never came into general use. He was a man of extensive learning, and made so rapid a progress in the sciences, when attending the university of Paris, that he was esteemed the glory of that seat of learning. He prosecuted his favourite study of experimental philosophy with unremitting ardour; and in this pursuit, in the course of twenty years, he expended no less than £2000 in experiments, instruments, and inprocuring scarce books. In consequence of such extraordinary talents, and such astonishing progress in the sciences, in that ignorant age, he was represented, by the envy of his illiterate fraternity, as having dealings with the devil; and, under this pretence, he was restrained from reading lectures, and at length, in 1278, when sixty-four years of age, he was imprisoned in his cell, where he remained in confinement for ten years. He shone like a single bright star in a dark hemisphere—the glory of our country—and died at Oxford, in the year 1294, in the eightieth year of his age. ‘Friar Bacon,’ says the Rev. Mr. Jones, ‘may be considered as the first of English philosophers; his profound skill in mechanics, optics, astronomy, and chemistry, would make an honourable figure in the present age. But he is entitled to further praise, as he made all his studies subservient to theology, and directed all his writings, as much as could be, to the glory of God. He had the highest regard for the sacred scriptures, and was persuaded they contain the principles of all true science.’
The next person who is supposed to have acquired a knowledge of telescopes, was Joannes Baptista Porta, of Naples, who flourished in the sixteenth century. He discovered theCamera Obscura—the knowledge of which might naturally have led to the invention of the telescope; but it does not appear that he ever constructed such an instrument. Des Cartes considers James Metius, a Dutchman, as the first constructor of a telescope, and says, that ‘as he was amusing himself with making mirrors and burning-glasses, he casually thought of looking through two of his lenses at a time, and found that distant objects appeared very large and distinct.’ Others say that this greatdiscovery was first made by John Lippersheim, a maker of spectacles at Middleburg, or rather by his children, who were diverting themselves with looking through two glasses at a time, and placing them at different distances from each other. But Borellus, who wrote a book ‘on the invention of the telescope,’ gives this honour to Zacharias Jansen, another spectacle-maker in the same town, who, he says, made the first telescope in 1590. Jansen was a diligent inquirer into nature, and, being engaged in such pursuits, he was trying what use could be made of lenses for those purposes, when he fortunately hit upon the construction. Having found the arrangement of glasses which produced the effect desired, he enclosed them in a tube, and ran with his instrument to prince Maurice, who, immediately conceiving that it might be of use to him in his wars, desired the author to keep it a secret. Such are the rude conceptions and selfish views of princelywarriors, who would apply every invention in their power for the destruction of mankind. But the telescope was soon destined to more noble and honourable achievements. Jansen, it is said, directed his instrument towards celestial objects, and distinctly saw the spots on the surface of the moon, and discovered many new stars, particularly seven pretty considerable ones in the Great Bear. His son Joannes is said to have noted the lucid circle near the lower limb of the moon, now namedTycho, from whence several bright rays seem to dart in different directions. In viewing Jupiter, he perceived two, sometimes three, and at the most four small stars, a little above or below him, and thought that they performed revolutions around him. This was, probably, the first observation of the satellites of Jupiter, though the person whomade it was not aware of the importance of his discovery.17
It is not improbable that different persons about Middleburgh hit upon the invention, in different modes, about the same time. Lippersheim seems to have made his first rude telescope by adjusting two glasses on a board, and supporting them on brass circles.18Other workmen, particularly Metius and Jansen, in emulation of each other, seem to have made use of that discovery, and by the new form they gave it, made all the honour of it their own. One of them, considering the effects of light as injurious to distinctness, placed the glasses in a tube blackened within. The other, still more cautious, placed the same glasses within tubes capable of sliding one in another, both to vary the prospects, by lengthening the instrument, according to the pleasure of the observer, and to render it portable and commodious. Thus, it is probable that different persons had a share in the invention, and jointly contributed to its improvement. At any rate, it is undoubtedly to the Dutch that we owe the original invention. The first telescope made by Jansen, did not exceed fifteen or sixteen inches in length, and therefore its magnifying power could not have been very great.
The famous Galileo has frequently been supposed to have been the inventor of the telescope, but he acknowledges that he had not the honour of being the original inventor, having first learnedfrom a German, that such an instrument had already been made; although, from his own account, it appears that he had actually re-invented this instrument. The following is the account, in his own words, of the circumstances which led him to construct a telescope. ‘Nearly ten months ago (namely in April or May 1609) it was reported that a certain Dutchman had made a perspective through which many distant objects appeared distinct as if they were near: several effects of this wonderful instrument were reported, which some believed and others denied: but, having it confirmed to me a few days after by a letter from the noble John Badoverie, at Paris, I applied myself to consider the reason of it, and by what means I might contrive a similar instrument, which I afterwards attained to by the doctrine of refractions. And, first, I prepared a leaden tube, to whose extremities I fitted two spectacle-glasses, both of them plain on one side, and on the other side, one of them was spherically convex, and the other concave. Then applying my eye to the concave, I saw objects appear pretty large and pretty near me. They appeared three times nearer and nine times larger in surface than to the naked eye: and soon after I made another, which represented objects about sixty times larger, and eight times nearer; and, at last, having spared no labour nor expense, I made an instrument so excellent, as to show things almost a thousand times larger, and above thirty times nearer, than to the naked eye.’ In another part of his writings, Galileo informs us that ‘he was at Venice when he heard of Prince Maurice’s instrument, but nothing of its construction; that the first night, after he returned to Padua, he solved the problem, and made his instrument the next day; and soon after, presentedit to the Doge at Venice, who, to do him honour for his grand invention, gave him the ducal letters which settled him for life in his lectureship at Padua; and the Republic, on the twenty-fifth of August in the same year (1610) more than tripled his salary as professor.’
The following is the account which this philosopher gives of the process of reasoning, which led him to the construction of a telescope:—‘I argued in the following manner. The contrivance consists either of one glass or more—one is not sufficient, since it must be either convex, concave, or plane; the last does not produce any sensible alteration in objects, the concave diminishes them; it is true that the convex magnifies, but it renders them confused and indistinct; consequently one glass is insufficient to produce the desired effect. Proceeding to consider two glasses, and bearing in mind that the plane glass causes no change, I determined that the instrument could not consist of the combination of a plane glass with either of the other two. I therefore applied myself to make experiments on combinations of the two other kinds; and thus obtained that of which I was in search.’ If the true inventor is the person who makes the discovery by reasoning and reflection, by tracing facts and principles to their consequences, and by applying his invention to important purposes, then, Galileo may be considered as the real inventor of the telescope. No sooner had he constructed this instrument—before he had seen any similar one—than he directed his tube to the celestial regions, and his unwearied diligence and ardour were soon rewarded by a series of new and splendid discoveries. He descried the four satellites of Jupiter, and marked the periods of their revolutions; he discovered thephases of Venus, and thus was enabled to adduce a new proof of the Copernican system, and to remove an objection that had been brought against it. He traced on the lunar orb, a resemblance to the structure of the earth, and plainly perceived the outlines of mountains and vales, casting their shadows over different parts of its surface. He observed, that when Mars was in quadrature, his figure varied slightly from a perfect circle; and that Saturn consisted of a triple body, having a small globe on each side—which deception was owing to the imperfect power of his telescope, which was insufficient to show him that the phenomenon was in reality a ring. In viewing the sun, he discovered large dark spots on the surface of that luminary, by which he ascertained that that mighty orb performed a revolution round its axis. He brought to view multitudes of stars imperceptible to the naked eye, and ascertained that those nebulous appearances in the heavens which constitute the Milky Way, consist of a vast collection of minute stars, too closely compacted together to produce an impression on our unassisted vision.
The results of Galileo’s observations were given to the world in a small work, entitled ‘Nuncius Sidereus,’ or, ‘News from the starry regions,’ which produced an extraordinary sensation among the learned. These discoveries soon spread throughout Europe, and were incessantly talked of, and were the cause of much speculation and debate among the circles of philosophers. Many doubted; many positively refused to believe so novel and unlooked-for announcements, because they ran counter to the philosophy of Aristotle, and all the preconceived notions which then prevailed in the learned world. It is curious, andmay be instructive, to consider to what a length of absurdity, ignorance and prejudice carried many of those who made pretensions to learning and science. Some tried to reason against the facts alleged to be discovered, others contented themselves, and endeavoured to satisfy others, with the simpleassertionthat such things were not, and could not possibly be; and the manner in which they supported themselves in their incredulity was truly ridiculous. ‘O my dear Kepler,’ says Galileo in a letter to that astronomer, ‘how I wish we could have one hearty laugh together. Here at Padua is the principal professor of philosophy, whom I have repeatedly and urgently requested to look at the moon and planets through my glass, whichhe pertinaciously refuses to do, lest his opinions should be overturned. Why are you not here? what shouts of laughter we should have at this glorious folly! and to hear the professor of philosophy at Pisa labouring with the Grand Duke with logical arguments, as if with magical incantations, to charm the new planets out of the sky.’ Another opponent of Galileo, one Christmann, says in a book he published, ‘We are not to think that Jupiter has four satellites given him by nature, in order, by revolving round him, to immortalize the Medici who first had notice of the observation. These are thedreams of idle men, who love ludicrous ideas better than our laborious and industrious correction of the heavens. Nature abhors so horrible a chaos; and to the truly wise, such vanity is detestable.’ One Martin Horky, a would-be philosopher, declared to Kepler, ‘I will never concede his four new planets to that Italian from Padua,though I should die for it;’ and he followed up this declaration, by publishing a book against Galileo, in which heexamines four principal questions respecting the alleged planets; 1. Whether they exist? 2. What they are? 3. What they are like? 4. Why they are? The first question is soon disposed of by declaring positively that he has examined the heavens with Galileo’s own glass, and that no such thing as a satellite about Jupiter exists. To the second, he declares solemnly that he does not more surely know, that he has a soul in his body than that reflected rays are the sole cause of Galileo’s erroneous observations. In regard to the third question, he says, that these planets are like the smallest fly compared to an elephant; and finally, concludes on the fourth, that the only use of them is to gratify Galileo’s ‘thirst of gold,’ and to afford himself a subject of discussion. Kepler, in a letter to Galileo, when alluding to Horky, says, ‘He begged so hard to be forgiven, that I have taken him again into favour upon this preliminary condition—that I am to show him Jupiter’s satellites,AND HE IS TO SEE THEM, and own that they are there.’
The following is a specimen of the reasoning of certain pretended philosophers of that age against the discoveries of Galileo. Sizzi, a Florentine astronomer, reasons in this strain: ‘There are seven windows given to animals in the domicile of the head, through which the air is admitted to the rest of the tabernacle of the body to enlighten, to warm and to nourish it; two nostrils, two eyes, two ears, and a mouth; so in the heavens, or the great world, there are two favourable stars, two unpropitious, two luminaries, and Mercury alone undecided and indifferent. From which and many other similar phenomena in nature, such as the seven metals, &c., we gather that the number of planets isnecessarily seven. Moreover,the satellites are invisible to the naked eye, and therefore can exert no influence on the earth, and therefore would be useless,and therefore do not exist. Besides, as well the Jews as other ancient nations have adopted the division of the week into seven days, and have named them from the seven planets. Now, if we increase the number of the planets, this whole system falls to the ground.’ The opinions which then prevailed in regard to Galileo’s observations on the moon, were such as the following:—Some thought that the dark shades on the moon’s surface arose from the interposition of opaque bodies floating between her and the sun, which prevent his light from reaching those parts; others imagined that, on account of her vicinity to the earth, she was partly tainted with the imperfections of our terrestrial and elementary nature, and was not of that entirely pure and refined substance of which the more remote heavens consist: and a third party looked on her as a vast mirror, and maintained that the dark parts of her surface were the reflected images of our earthly forests and mountains.
Such learned nonsense is a disgrace to our species, and to the rational faculties with which man is endowed, and exhibits, in a most ludicrous manner, the imbecility and prejudice of those who made bold pretensions to erudition and philosophy. The statement of such facts, however, may be instructive, if they tend to guard us against those prejudices and pre-conceived opinions, which prevent the mind from the cordial reception of truth, and from the admission of improvements in society which run counter to long-established customs. For the same principles and prejudices, though in a different form, still operate in society and retard the improvement of the social state,the march of science, and the progress of Christianity. How ridiculous is it for a man, calling himself a philosopher, to be afraid to look through a glass to an existing object in the heavens, lest it should endanger his previous opinions! And how foolish is it to resist any improvement or reformation in society, because it does not exactly accord with existing opinions, and with ‘the wisdom of our ancestors.’
It is not a little surprising, that Galileo should have first hit on that construction of a telescope which goes by his name, and which was formed with aconcaveglass next the eye. This construction of a telescope is more difficult to be understood, in theory, than one which is composed solely of convex glasses; and its field of view is comparatively very small, so that it is almost useless when attempted to be made of a great length. In the present day, we cannot help wondering that Galileo and other astronomers, should have made such discoveries as they did with such an instrument, the use of which must have required a great degree of patience and address. Galileo’s best telescope, which he constructed ‘with great trouble and expense,’ magnified the diameters of objects only thirty-three times; but its length is not stated—which would depend upon the focal distance of the concave eye-glass. If the eye-glass was two inches focus, the length of the instrument would be five feet four inches; if it was only one inch, the length would be two feet eight inches, which is the least we can allow to it—the object-glass being thirty-three inches focus, and the eye-glass placed an inch within this focus. With this telescope, Galileo discovered the satellites of Jupiter, the crescent of Venus, and the other celestial objects to which we have alreadyalluded. The telescopes made in Holland, are supposed to have been constructed solely ofconvexglasses, on the principle of the astronomical telescope; and, if so, Galileo’s telescope was in reality a new invention.
Certain other claimants of the invention of the telescope, have appeared, besides those already mentioned. Francis Fontana, in his ‘celestial observations,’ says, that he was assured by a Mr. Hardy, advocate of the parliament of Paris, a person of great learning and undoubted integrity, that on the death of his father, there was found among his things an old tube, by which distant objects were distinctly seen, and that it was of a date long prior to the telescope lately invented, and had been kept by him as a secret. Mr. Leonard Digges, a gentleman who lived near Bristol, in the seventeenth century, and was possessed of great and various knowledge, positively asserts in his ‘Stratoticos,’ and in another work, that his father, a military gentleman, had an instrument which he used in the field, by which he could bring distant objects near, and could know a man at the distance of three miles. Mr. Thomas Digges, in the preface to his ‘Pantometria,’ published in 1591, declares, “My father, by his continual painful practices, assisted by demonstrations mathematical, was able, and sundry times hath by proportional glasses, duly situate in convenient angles, not only discovered things far off, read letters, numbered pieces of money, with the very coin and superscription thereof, cast by some of his friends of purpose, upon downs in open fields, but also, seven miles off, declared what hath been done that instant, in private places. He hath also, sundry times, by the sun-beams, fired powder and discharged ordnance half a mile andmore distant, and many other matters far more strange and rare, of which there are yet living divers witnesses.”
It is by no means unlikely, that persons accustomed to reflection, and imbued with a certain degree of curiosity, when handling spectacle-glasses, and amusing themselves with their magnifying powers and other properties, might sometimes hit upon the construction of a telescope; as it only requires two lenses of different focal distances to be held at a certain distance from each other, in order to show distant objects magnified. Nay, even one lens, of a long focal distance, is sufficient to constitute a telescope of a moderate magnifying power, as I shall show in the sequel. But such instruments, when they happened to be constructed accidentally, appear to have been kept as secrets, and confined to the cabinets of the curious, so that they never came into general use; and as their magnifying power would probably be comparatively small, the appearance of the heavenly bodies would not be much enlarged by such instruments—nor is it likely that they would be often directed to the heavens. On the whole, therefore, we may conclude that the period when instruments of this description came into general use, and were applied to useful purposes, was when Galileo constructed his first telescopes.
Before proceeding to a particular description of the different kinds of telescopes, I shall first give a brief description of the Camera Obscura, as the phenomena exhibited by this instrument tend to illustrate the principle of a refracting telescope.
The termCamera Obscuraliterally signifies a darkened vault or roof; and hence it came to denote a chamber, or box, or any other place made dark for the purpose of optical experiments. The camera obscura, though a simple, is yet a very curious and noble contrivance; as it naturally and clearly explains the manner in which vision is performed, and the principle of the telescope, and entertains the spectator with a most exquisite picture of surrounding objects, painted in the most accurate proportions and colours by the hand of nature. The manner of exhibiting the pictures of objects in a dark room is as follows:—In one of the window-shutters of a room which commands a good prospect of objects not very distant, a circular hole should be cut of four or five inches diameter. In this hole an instrument should be placed, called aScioptric ball, which has three parts, a frame, a ball, and a lens. The ball hasa circular hole cut through the middle, in which the lens is fixed, and its use is, to turn every way so as to take in a view of objects on every side. The chamber should be made perfectly dark; and a white screen, or a large sheet of elephant paper, should be placed opposite to the lens, and in its focus, to receive the image. If then, the objects without be strongly enlightened by the sun, there will be a beautiful living picture of the scene delineated on the white screen, where every object is beheld in its proportions, and with its colours even more vivid than life; green objects appear in the picture more intensely green, and yellow, blue, red or white flowers appear much more beautiful in the picture than in nature; if the lens be a good one, and the room perfectly dark, the perspective is seen in perfection. The lights and shadows are not only perfectly just, but also greatly heightened; and, what is peculiar to this delineation, and which no other picture or painting can exhibit—themotionsof all the objects are exactly expressed in the picture; the boughs of the trees wave, the leaves quiver, the smoke ascends in a waving form, the people walk, the children at their sports leap and run, the horse and cart move along, the ships sail, the clouds soar and shift their aspects, and all as natural as in the real objects; the motions being somewhat quicker, as they are performed in a more contracted scene.
These are theinimitableperfections of a picture, drawn by the rays of light as the only pencil in nature’s hand, and which are finished in a moment; for no sensible interval elapses before the painting is completed, when the ground on which it is painted is prepared and adjusted. In comparison of such a picture, the finest productions of the most celebrated artists, the proportionsof Raphael, the natural tints and colouring of Titian, and the shadowing of the Venetians, are but coarse and sorry daubings, when set in competition with what nature can exhibit by the rays of light passing through a single lens. The Camera obscura is at the same time the painter’s assistant, and the painter’s reproach. From the picture it forms he receives his best instructions, and is shown what he should endeavour to attain; and hence, too, he learns the imperfections of his art, and what it is impossible for him to imitate. As a proof of this, the picture formed in the dark chamber will bear to be magnified to a great extent, without defacing its beauty, or injuring the fineness of its parts; but the finest painted landscape, if viewed through a high magnifier will appear only as a coarse daubing.
The following scheme will illustrate what has been now stated respecting the dark chamber. EF represents a darkened room, in the side of which, IK, is made the circular hole V, in which, on the inside, is fixed the scioptric ball. At some considerable distance from this hole is exhibited a landscape of houses, trees, and other objects, ABCD, which are opposite to the window. The rays which flow from the different objects which compose this landscape, to the lens at V, and which pass through it, are converged to their respective foci, on the opposite wall of the chamber HG or on a white moveable screen placed in the focus of the lens, where they all combine to paint a lively and beautiful picture of the range of objects directly opposite, and on each side, so far as the lens can take in.
Though I have said, that a scioptric ball and socket are expedient to be used in the above experiment, yet where such an instrument is not athand, the lens may be placed in a short tube made of pasteboard or any other material, and fixed in the hole made in the window shutter. The only imperfection attending this method is, that the lens can exhibit those objects only which lie directly opposite the window.