this salt is dissolved in perfectly pure distilled water, it may be exposed to sunshine for any period without undergoing change; but add thereto the smallest portion of organic matter, and it is quickly decomposed, the silver being precipitated as a black powder. In paper we have the required organic principle, and if we wash a sheet with the solution of nitrate of silver, and expose it with any body superposed-say a fern-leaf-all the parts which are exposed will blacken, those screened will remain white, and thus there will be produced what is called a negative image. Chloride of silver, obtained by washing the paper, first with a weak solution of common salt and then with nitrate of silver, is a far more sensitive photographic agent, and is now commonly employed. The Calotype process of Mr. Fox Talbot consists in washing paper, first with todide of potassium, and then with nitrate of silver, by which process is obtained an iodide of silver. The paper should contain nothing but this iodide; therefore all soluble salts are removed by soaking in water. This pale primrose-color paper, which is not sensitive to light, is washed with a peculiar organic salt called gallic acid; and, to increase the instability of the preparation, a little nitrate of silver is added to it, producing what the inventor calls a gallo-nitrate of silver. Here we have a preparation already quick with chemical energy; this is applied to the iodized paper, and the chemical power of the sun, as radiated from external objects, instantly produces a change-that change bearing an exact relation to the intensity of the rays falling upon each portion of the light-created picture. Presently a picture becomes visible, and it is increased in intensity by washing it, in the dark, with a fresh portion of the gallic acid solution. The picture thus obtained is fixed by washing it with a salt, which dissolves the iodide or the chloride of silver, which has not undergone change -the hyposulphite of soda-and subsequently soaking in clean water. The Daguerreotype consists in producing an iodide of silver upon the surface of a polished silver-plate, and receiving the camera image upon this prepared surface. In both of these processes a decomposition of the iodide of silver results; but in Daguerre's process, the image is developed by exposing the plate on which it has been impressed to the vapor of mercury. Mercury combines with metallic silver, but not with the iodide; thus it is deposited over every portion of the plate on which the solar radiations have acted—the thickness of the deposit bearing a strict relation to the intensity of chemical effect produced. This picture is also fixed by the use of the hyposulphite of soda; as, indeed, are nearly all varieties of photographic pictures. By modifications, which cannot be here detailed, these processes have been greatly increased in sensibility; the result which formerly required twenty minutes being now obtained in as many seconds. A process more sensitive than either of those named has extended photography in a most remarkable manner-this is the COLLODION process. Collodion is guncotton dissolved in ether; to this is added some iodide of potassium dissolved in spirits of wine. This iodized collodion is poured over a sheet of glass-the ether evaporating leaves a beautiful film on the surface, which, upon the glass being dipped into a solution of nitrate of silver, becomes exquisitely sensitive. This prepared tablet being placed in the camera receives an image almost instantaneously, which is brought out in full vigor by pouring over it a solution of the proto-sulphate of iron or of pyro-gallic acid. The exquisite perfection of the collodion pictures, dependent upon the rapidity with which the images are impressed, is mainly due to the peculiar conditions of this singular preparation. By a preparation in many respects analogous to the collodion, a degree of sensibility far exceeding anything which the most sanguine photographist dreamed of in his ardent moments has been obtained. A plate prepared with albumen, iodide of iron, and alcohol, and acetic acid, was placed in a dark room of the Royal Institution in a camera obscura; opposite to it, at the proper focal distance, was a wheel, which was made to revolve many hundred times in a second, and this wheel carried a printed bill upon its face. This rapidly-revolving placard was illuminated for a moment by a flash from a Leyden jar. When the prepared plate was examined by means of a developing agent, it was found, that notwithstanding the rapidity with which the image moved over the lens and the transient nature of the light, a picture of the printed bill was clearly formed, with the letters perfect. This was an experiment of Mr. Fox Talbot's, and is perhaps the most remarkable of the many examples of natural magic with which photography has brought us acquainted. It has long been a problem, the solution of which has been anxiously looked for, whether we might hope to obtain pictures in all the beauty of natural color. This has not yet been quite successfully accomplished; but the approaches toward it are so favorable that we may hope, in a few years, to find our photographic pictures colored by the agent which now draws them. That the delicate and fading images of the camera obscura should be permanently secured upon plates of metal and glass, and on paper, was, at one time, beyond the dreams of science. We rejoice in the reality, and nature herself paints for us the portrait of a friend, or those scenes which are endeared to us by the tenderest and most refined associations. We have now the means of obtaining the most truthful representations of the Pyramids and the tombs of Egypt. The Assyrian Excavation Society have realizations from the pencil of the sunbeam of all that remains of the great monarchies of the East. The traveler in Central America has secured, with his camera, pictures of the wonderful works of the Aztecs and the cotemporary races, of whom we know so little, but whose works remain to speak of a savage grandeur and an advanced state of art, rivaling that which we find in the palace of Sardanapalus and the temples of the early Pharaohs. The ethnologist rejoices in his collection of portraits from all parts of the world; in his quiet home he is enabled, by the aid of photography, to study the physiognomies of all the races on the face of the earth. The natural philosopher uses the same art to register for him the variations of atmospheric pressure and of the earth's temperature; more than this, the alterations in the magnetic intensity of this terrestrial globe are now faithfully registered by photography. The microscopist makes the light draw for him the details of organization, which it would be impossible for the human hand to trace. The astronomer places a sensitive tablet in his telescope; and not only does the sun draw his own image, but the milder moon traces out for him her mountains and her valleys, her beetling precipices, like old sea-coasts, and her dreadful volcanic craters, large and deep enough to swallow up all England. What, then, may we not expect from photography, with the advance of science? A few years since it was thought that two or three salts of silver and of gold were the only bodies which underwent any remarkable change when exposed to the action of the solar rays. It is now proved that it is not possible to expose any body, whatsoever may be its character, to the action of sunshine without its undergoing a chemical or a mechanical change. For example, take a plate of glass, of metal, of stone, or a surface of leather, or resin,-in fact, any organic or inorganic body,—and placing a perforated screen above it, expose it for a a short time to solar influence; then treating the plate as we do the Daguerreotype, exposing it to the vapor of mercury,— we shall find a picture of the superposed screen most faithfully made out on the surface; proving thus that it is impossible to expose any substance to sunshine without its undergoing a change; and that constant sunshine would be destructive to the permanence of matter, as now constituted. It has, however, been found that Nature has a beautiful provision for restoring the deranged conditions. During darkness, by the action of some peculiar molecular forces, all bodies possess the power of restoring themselves to the state in which they were previously to the destructive action of the sunshine; and as night and repose are required to restore to the animal and vegetable economy the vital forces which have become exhausted by the labors of the day, and the excitements which depend upon light, so are night and darkness required to insure the permanence of the inorganic masses of the earth's surface. Can there be a more beautiful provision than this? The laws by which the Eternal Creator works are indeed wonderful and grand; the study of creation's mysteries induces a refinement of the mind, and a holy tranquillity of spirit. No one can arise from reading a page of Nature's mighty volume without feeling himself to be "A wiser and a better man." I SIR LOG AND HIS COUSIN. are brought into such close fellowship, we may as well make acquaintance; and as there is no master of the ceremonies at hand, and I, as I take it, am the elder, I will just introduce myself to you as a branch of the Oak family—one of a very ancient and distinguished tribe-only some twelve or fourteen generations removed from the first of that noble family who flourished in the days of Adam and Eve, and of unbroken and untarnished descent-a true scion of an ancient stock. And now, my young friend, allow me to crave your name and history?" added Sir Log, in a patronizing manner. WAS sitting by my fireside, one evening in November, dreaming in the twilight; but whether they were sleeping or waking dreams in which I indulged, I shall leave it to those who may read my story to decide, without myself offering any opinion on the subject. A capital fire shone on the hearth, and lit up the walls of the antique library in which I sat, flickering among the carved work of the dark oak ceiling and wainscoting, and occasionally lighting up the lofty ancient mantelpiece, which was decorated with the heraldic devices of the former owners of the hall- men who had ages since moldered in the tomb. The wide, oldfashioned grate contained an abundant supply of fuel, part of it being filled with good Newcastle coal, throwing out plenty of fine rich fatty matter, from which is-auricular cavities of the wood. sued at intervals, as from petty volcanoes, "I beg your pardon, sir," responded jets of gaseous smoke and flame; while | Sir Log, with some warmth, "I meant no in the arms of this mass of fire lay a huge offense; but really, as the senior, and oaken log, inwreathed in its own brilliant with my pedigree, I thought -. Perflames, emitting from time to time showers haps you are not aware that I am some of sparks, and as it were sportively darting four or five hundred years old?" long tongues of serpent-like blue and amber flame through every possible vent, now withdrawing them for a moment, and then pouring forth a fresh volume with renewed vigor and splendor. As I sat, enjoying the warmth, and dreamily watching these evolutions, I began to trace a sort of understanding between the wood and the coal, as if they were getting into a chat, and by degrees to make out, or fancy that I made out, what they said to each other. How I came to understand the conversation, I cannot exactly explain; but it is no more wonderful that I should do so, than that the vizier in the eastern tale should be able to inform the sultan of the consultations which were taking place among the birds. It may be supposed, if the reader likes, that there is some affinity between me and a log of wood; and really I cannot say but that it may be so—all that I can do is, like a faithful chronicler, to narrate my tale, and leave others to draw their own deductions from it. I will therefore tell what passed that evening, not at my fireside, but in the very heart and depths of my fire. "Well, my boy, how are you to-day?" crackled out the wood; "methinks, as we A low murmuring sound, followed by a considerable ebullition of smoke and flame, burst from the offended coal. "Boy, indeed! young friend!" and something very like "Upstart mushroom!" fell on my ear, though luckily it did not strike on the "Senior! pedigree!" broke in the fiery old gentleman; "four or five hundred years old! why, I am more likely four or five hundred thousand years old; and as to pedigree, I am Lord Carbonius, one of old King Coul's family, as it were part and parcel of himself." "O, indeed!" replied Sir Log, reverentially. "I have been used to the society of kings and great men, and know how to reverence them. I grew near a royal residence myself, and often have the kings and queens of England stood and sat under my spreading branches. Some of the greatest men of their day have given me their confidence, and held consultations under my shadow; and royal armies have been mustered, ay, and broken up and defeated, in my sight." "And I grew and flourished ages on ages before that pigmy called manwhether king or boor, prince or peasant— was created, or had a name in the earth! Ages before his race was formed, I lived in majestic grandeur, and formed part of a stately pine, such as earth now knows not either in kind or size. Around me grew interminable forests of trees as splendid as myself, chiefly palms and pines; while club - mosses, horse - tails, and other plants of quite different tribes from those which now decorate the earth, and of a size which would have pretty well choked up your kinds, surrounded me." "But, if this is so, where have you been ever since, my lord ?" asked Sir Log. "Down, down in the depths of the earth, at rest," replied Carbonius. "How long I have lain there I know not; but this I know, that there I should have been to this hour but for the being you call man, who seems to have power to wrench all her long-hidden secrets from nature, and to apply all her long-hoarded treasures to his own special use and emolument. He, by his skill and wisdom, conquered all the defenses which have so long shielded me and my other mineralized friends from disturbance, overcame the many dangers and difficulties which arose from the deadly gases and devouring subterranean waters which guarded our dismal prisonhouses, and brought us up once more to the light of day." 66 'Well, well," quoth old Carbonius, "I have no objection—let it be we if you like; indeed, there is some little connection between us, though we are of different families. But there are other branches of the Carbon family beside myself who make no small noise in the world, both as useful and ornamental articles. There are my cousins Jet, a worthy family, though a little of the melancholy complexion; but the Diamonds! O, they are the most illustrious by far of our tribe; and they are sterling, sound-hearted creatures, too, and most intrinsically valuable, never ashamed to recognize an old friend; and never do they look more bright and attractive than when their brilliant countenances reflect a glance of recognition from me, comparatively humble as is the position in life which I now occupy!" "You speak like an oracle, my lord,” said Sir Log, who had become wonderfully respectful since he found "Old Ebony,” as he had irreverently called his com "And here we lie now, both together," responded Sir Log; "you of an ante-mundane, and I of a post-diluvian formation, fast dwindling away into dust and ashes; and so will end my pedigree and yours-panion, was so highly connected; "but it my five hundred years, and your five hundred thousand." "Not so," replied the old dignitary; "that is a youthful mistake on your part. I thought myself, when in that grand combustion of the elements which ended my then state of existence-when, with many thousands of my congeners, I vanished from the face of the earth, and was inclosed by the masses of matter which overwhelmed us-that there was surely an end of me. Who would have thought that, after unknown ages, (for none can number them; not the wisest among men, with all his learning, can answer the simple question, 'When and how was the coal formation deposited ?")—who, I say, would have thought of my ever again becoming an inhabitant of the upper regions? of my going through a new stage of existence and of usefulness? of my being so important to man, that, without my help, many of his most noble works could not go forward? nay, more, of my becoming one of the brightest ornaments of his saloons, 'the cynosure of neighboring eyes,' the center of attraction to all who enter my presence ?" seems to me that both you and I are fast falling to ashes, and in that state we are not likely to have 'greatness thrust upon "Young again!" growled out old Carbon, rather snappishly; "why, my good friend, you are quite boyish. I maintain that there is not a particle of either you or me that falls from this grate that will not in some way or other turn to use. We must bide our time.' We have now had our day of brightness and honor, and next will come a time of apparent degradation; but do not be discouraged; it is all needful to prepare us for our future exaltation; even the fire which is now eating out our vitals is aiding in the work. We shall be cast out on the face of the earth; then by degrees will come a change-we shall be decomposed, as it is called; that is, all our component parts will be dissolved, separated, and each applied to its own special use in chemically altering the nature of the earth with which we are mixed, fitting it for the growth of vegetables, which will absorb, and feed on our different alkaline salts, &c.,-by this means we shall impart to them their va from day to day? I used to think that man could do everything; and, to hear some of them talk, one would suppose that they thought so themselves; but as you say that you existed ages before man was formed, he can have had no hand in making you, or preparing you for your pre rious flavors and qualities; these vegetables in their turn will nourish man and beast, and thus we shall again have our day of honor; after which we shall return back to the lower stages of our existence, again hereafter to ascend; and so goes on the round of wondrous changes, every particle of created matter having its mis-sent uses.' sion, and fullfilling it in its appointed "Man is very wise," replied old Carcourse." "But stay a minute, great philosopher," wheezed the now almost exhausted Wood; “as you talk, puff, puff, goes your breath up the chimney, and now and then, when you are especially emphatic, a portion of it escapes into the room, and deposits sundry black particles on the furniture and walls; you do not mean to say that those blacks and that smoke will ever turn to use." "Every particle of it, every particle!" shouted old Carbonius, vehemently. "Did you never see heaps of soot placed on the fields, even within sight of the royal domain in which you say you grew? Well, this soot, like the ashes, is decomposed, and in the same manner supplies nourishment to the vegetable, and through it to the animal creation. Those particles of our life-breath which are not deposited in the chimney, float away into the air, or unite themselves with it; and they, too, have their mission. It is a wonderful thought, but follow it out, and you will find what I say to be true: that not one particle of matter has ever existed which has not had, and continues to have, some part to play in the cosmogony of this wide world; not one which does not avail for some purpose or other; nor one which has ever faded into nothing, or ceased, in some form or other, to exist. Infinite, wonderful are the changes which take place in their modes of existence that which at one time forms an integral part of a solid body, at another becomes an invisible, ethereal fluid-one of the subtile essences which circulate in air, water, or some other portion of the material world; while that which was a mere floating gas becomes in its turn absorbed into a human or other living body, and for a time forms a part of its vital existence; but nothing utterly perishes, nothing ever has perished." "One question more, my lord," said Sir Log. "Tell me who contrived this wonderful mechanism-who carries it on bonius. "He can rend her secrets from He Thine, O Lord, is the greatness, and the power, and the glory,' and 'there is no end of thy greatness! "I am glad," sighed forth Sir Log, as, with a dying sparkle, his last embers fell on the hearth, "very glad that some day we shall be great again! [For the National Magazine.] RAIN-DROPS. SWEET visitants of earth, Like brightly-sparkling gems, Or fall to earth unseen, Dance down to valleys green. Where is the path ye go, I saw ye yesternight But ye are wrecks to-day, D. WILLIAMS. |