in the year 1781, and was found to extend both to solids and liquids passing into a gaseous form."* PROPOSITION V. Light is capable of conferring an attractive power upon glass. If a glass jar, containing camphor, be placed in a window, beautiful crystals will attach themselves to the sides nearest to the light. Evidence of this fact may frequently be seen in druggists' shops. Many other substances, which are capable of the same kind of sublimation, exhibit the same phenomena in their solidification."+ M. Chaptal first made the observation "That when a number of capillary crystals shoot up the sides of a glass vessel containing a saline solution, they attach themselves only to that side of the vessel which is most strongly illuminated. He was thus able to cause crystals to form on any selected side; and by placing a screen before the vessel he found that the line between light and darkness was distinctly marked by the limit of crystallization. This result is most readily obtained with the metallic salts." Let us now ascertain how far these several facts, embodied in the foregoing propositions, will serve to explain the phenomena of the daguerreotype; and in order to do this, we must follow the process from its very commencement. The first step in our process, then, is to prepare a highly polished silver tablet, which is a conductor of electricity. This prepared tablet is then placed in a box containing a small quantity of iodine, a non-conductor of electricity."§ The vapour of iodine rises; and we know, by the fact embodied in our fourth proposition, that it is charged with electricity. The first film of iodine which is deposited upon the plate loses its electricity by coming in contact with a conducting surface of silver; but the after portions of condensed vapour retain their electricity, for they do not fall upon the conducting silver, but upon the film of nonconducting iodine, which has just been deposited. The result, then, of the first operation is the production upon the silver tablet of a non-conducting surface, the upper portions of which are charged with electricity. Now, instead of at once transferring this prepared plate to the camera, let it be submitted to the vapour of inercury in the ordinary way-but no mercury will adhere to it. The conclusion is irresisti ble. The vapour of mercury we know to be electrified (proposition iv), and its electricity is evidently similar to that of the prepared tablet; therefore it is repelled by it (proposition ii). Let us now return to the generally adopted process : The plate is placed in the focus of a camera obscura, where it remains exposed to the action of light for a certain period of time. It • Dr. Roget's Treatise on Electricity, page 55. + Daniel's Elements of Chemical Philosophy, page 399. is then submitted to the vapour of mercury, not, however, with the same result as before. The mercury is now no longer repelled by those portions of the tablet which have been submitted to a strong light, but is attracted and accumulated there in exact proportion to the degree of action which has taken place at these several points. The plate may now be exposed with safety to the light, even before the coating is washed away; for, as we do not wish again to expose it to the vapour of mercury, the electrical condition of its surface is perfectly immaterial.* From a consideration of the several points enumerated above, it follows, that when the charged plate is exposed to the action of light, its electricity is lowered, or totally destroyed, in the illuminated parts, and its repulsion to the vapour of mercury no longer maintained. It would appear, too, from the foregoing propositions, that light itself is either the same with electricity, or that it has the power of exciting that agency in the bodies upon which it falls; for, by our third proposition, we find that "positive electricity can only be neutralized by negative, and negative by positive." If therefore, we once determine the nature of the electricity of the vapour of iodine or of mercury, we can readily ascertain that of light, for it must be of the opposite kind. Such then, given in his own words, are Mr. Baggs's views of the phenomena of the daguerreotype. That the propositions upon which his reasoning is founded are correct and well established, no one will for a moment doubt. The question, therefore, is, are the deductions from the facts embodied in the data sound and logical, and will they bear the test of close and accurate experiment? If Mr. Baggs's theory be correct, much will be accomplished in the elucidation of some of the most profound mysteries of science. We wish he would still continue his researches in this important matter, nor rest content with the mere outworks of the question. We would venture to remind him of the words placed by Juvenal in the mouth of the one-eyed Hannibal when he had overcome the rugged passes of the Alps, and already stood upon the plains of Italy. "Actum, inquit, nihil est nisi Pano milite portas February, 1842. EARTHQUAKES, ELECTRIC STORMS, ETC. ON Sunday morning, Feb. 9, this town and the vicinity was visited with one of the most terrific thunder and lightning storms recollected even by the very oldest inhabitants. About seven In detailing the steps of the process, Mr. Baggs, for the sake of simplicity, merely refers to the employment of iodine as the sensitive material. that being the substance originally used by Daguerre. The employment of the sensitive compound of chlorine and iodine, however, could not at all affect the truth of the author's propositions. o'clock, A.M., the wind commenced blowing a perfect hurricane from the N.N.W., the rain and large hailstones descending in torrents, and deluging the face of the country. Loud peals of thunder and vivid flashes of lightning followed in close succession, and continued for nearly five hours. Several houses in Milebush were blown down; and the electric fluid killed half a dozen sheep and pigs in the parish of Breaffy. Throughout different parts of the country we understand that the injury done to cattle and poultry has been very considerable; but happily, so far as we have been able to ascertain, there was no destruction of human life. During the continuance of the gale, it blew more powerfully than during the memorable storm of January, 1839.-Mayo Telegraph. An Earthquake in Cornwall. A report has been drawn up by Mr. Hunt, for the Polytechnic Society, of the particulars of the earthquake felt in Cornwall, on the 17th of February last; from which we collect the following particulars-In the neighbourhood of Falmouth the noise attracted attention, although but few persons felt any tremulous motion. At Penryn the disturbance was more decidedly felt, doors were shaken and the earthenware rattled on the shelves. At Roosanooth, and down the valley, the shock was considerable, and the first impression was that the powder mills in the neighbourhood had exploded. The inhabitants of the villages of Comfort and Lammer, about the junction of the granite and killas, or clay slate, left their houses, thinking that some serious explosion had occurred at the neighbouring mine. At Cann Marth, a widow woman ran out shrieking that the side of her house was falling in. In Poldory, the shock was felt by the men working 130 fathoms below the surface. In other places it was felt even more intensely; and at Constantine doors flew open, persons were shaken in their beds, and some men working in the house ran out to know what was the matter. At Helstone the disturbance was considerable. At West Wheal mine, men at work in the 100 fathom level felt a shock, and, as it were, a rush of air; so much so that one of the candles was put out by it, accompanied by a noise which made them think that one of the shafts had crushed in. This appears to have been the most westerly part at which the tremor was felt, although the noise was heard further, but in diminished force. Mr. Hunt states that, on referring to a geological map of the county, it will be found that the greatest effects were produced near the edge of the granite mass, which extends from the north-east to the south-west; from Cann Marth to the south of Penryn. Although it was felt at Falmouth, Helstone, and other places, which are on the clay slate, yet all his inquiries went to show that it diminished rapidly in force as the distance from the granite increased. A Factory Chimney Struck by Lightning. During the thunder storm which visited this neighbourhood, on Sunday afternoon, Feb. 27, a chimney, in the yard of the cotton mill of Messrs. Carr and Co., Heaton Lane, Stockport, was struck by lightning. The chimney, which is octagonal and of recent erection, stands detached in the middle of the factory yard, and is about seventy yards high. The electric fluid broke the cornice of the chimney, taking with it a number of the inside and outside bricks, and descended down an external angle, tearing the brickwork from the fabric to the breadth of fifteen or twenty inches, and eight or ten yards in length. For eight or ten yards lower down, the chimney is not perceptibly injured; but at that distance the outside brickwork is again torn off, perhaps to the breadth of two feet, and a yard and a half or two yards in length. Seven or eight yards lower down, but not in a parallel line, is a somewhat similar fracture, after which no other damage is perceptible on the outside. What may be the injury to the inside of the chimney has not yet been ascertained, it not having yet been examined. The occurrence will not throw any hands out of employ during repairs, as the mill has been closed several months. Destructive Earthquake in St. Domingo. The following account of a most frightful and destructive earthquake in the island of St. Domingo is given by the New York Morning Courier, from a Port-au-Prince paper of the 11th of May : On Saturday, the 7th inst., at twenty minutes past seven in the evening, we experienced some severe shocks of an earthquake, which put the whole town in commotion. At midnight a thick meteor was perceived passing to the east. The heat was excessive, and thick clouds hung over the neighbouring mountain, going in a direction from the south-east to the north-east. The seamen who were in the roads report that they felt the shock before they saw the houses shake, which would indicate that the shock came from the east. Many persons, however, think that the oscillations came from the north and went south. There were two very decided shocks, the first was not so long as the second; the latter was the most violent, and lasted about three minutes. All abandoned their houses, and the streets were filled with the affrighted population. But a little more, and Port-au-Prince would have been the scene of a disaster similar to that of 1770, a fatal year, which occurred to the minds of every one. There is scarcely a single brick or stone house which has not suffered damage; they are all more or less damaged. Some, it is said, are scarcely habitable. The facade of the Senate House, on which is sculptured the arms of the republic, surmounted by the tree of liberty, were detached from the edifice, and broken into pieces by the fall. The interior of the building has also received some damage. In the night, between Saturday and Sunday, two shocks were again felt; but not as violent as the first; one at 10 o'clock, and the other at 12. At 11 o'clock in the morning of Sunday came another shock: mass at church was interrupted, and those officiating at it ran away, and many females fainted. Monday, at 11 o'clock in the morning, another shock. The weather, during these three days, had a lowering, and, at times, a threatening appearance. Monday evening, a little rain, with excessive heat before and afterwards; night cool. Tuesday, a change of weather; return of the breeze and appearance of rain. In the evening, at eight o'clock, the weather was stormy, and every thing seemed to indicate abundance of rain. The hopes we entertained yesterday have not been realized. On Wednesday we were awoke at a few minutes before five in the morning by another earthquake. During these latter days it appears to us as if the earth on which we were walking was constantly quaking. SAINT MARC.-A letter from this town, which has been communicated to us, informs us that there, too, the earthquake of Saturday last was felt with the greatest violence; many houses have been so much shaken that they threaten every instant to fall down. On some plantations, in the neighbourhood of the town very great damage has been done. GONAIVES, MAY 8.-Yesterday afternoon an earthquake was felt in this city, which was so violent that most of the houses in it were thrown down. At the same time, in consequence of the shock, a fire broke out in the apothecary's shop of Mr. Invernezzes, and consumed, in a few moments, an entire block. The flames destroyed everything that came in their way; there was not a drop of water in the town. All the houses which have not been burnt down have been injured by the earthquakes, and this morning the shocks occur every quarter of an hour. The shops of Madame John Joufferts and M. Dupuy have fallen a prey to the flames. The shops of M. Richard Dauphin and M. Oster, built of stone and brick, have fallen down. Houses and shops are inaccessible, and we write these hurried lines in the street. The whole population has passed the night in the middle of the streets. Of the merchandise, which the merchants had been obliged to pile up in the public square, a great part has been stolen. It is impossible at present to estimate the extent of the loss. The church, the prison, the national palace, the treasury, the arsenal, and the house which was getting ready for the colonel commanding this district, are now nothing more than a heap of ruins. In short, no one has escaped the calamity. Now, while we are writing, the fire is entirely extinguished; but the sky looks threatening, and we are afraid of more shocks. If, unfortunately, our fears should be realised, there will be an end of the few houses remaining standing, and Gonaives will be no more. The first and principal shock lasted about five minutes, and was followed, during |