over land, and become identified with tornadoes. Instances have occurred where they have crossed a river, and have taken up the contents of the stream, and distributed them over the neighboring country. Fish and mud have been thus raised from the bed of rivers, and scattered over the surrounding region. Although we have proofs that water spouts are whirlwinds, and we can accordingly assign to them the same laws, yet it is extremely difficult to assign the true cause of their formation. Like fame, "they stalk on earth, and hide their heads among the clouds." LECTURE VIII. Aurora Borealis. The Aurora Borealis exhibits a number of distinct varieties. In its simplest form, it has merely the appearance of a twilight in the north. In its more exalted forms, it shoots up into slender spindles called streamers- -or spans the heavens with a luminous arch-or forms a ringlet, called the corona, around a point a little southeast of the zenith, around which the streamers arrange themselves, as a common focus. In the more splendid exhibitions of the aurora, a large bank of light is first seen near the northern horizon, which afterwards sends forth streamers, flickering corruscations, and waves which flow with immense velocity, sometimes upwards towards the corona, and sometimes around the horizon, crossing the streamers apparently at a much lower elevation. These are called "Merry Dancers." Although similar exhibitions have occurred in all ages, and are often described in history, yet they have their periods;-for a number of years, usually not exceeding twenty, auroras are frequent and magnificent, and then are scarcely seen for fifty years or more. One of these periods embraced the era of the revolutionary war, and of the old French war; and another period, probably as brilliant as any on record, is now in progress, having commenced in the year 1827. The leading facts respecting the aurora are as follows: They are very frequent and splendid in the polar regions; but are seldom seen at all below the latitude of forty degrees. They are seen over an immense extent at the same time. The aurora of September 3d, 1839, was seen, almost in equal magnificence, at London, in Canada, at New York, and at New Orleans. Hence its height must, sometimes at least, be very great. Estimates carry it as high as fifty or sixty, or even one hundred miles. The aurora has singular magnetic properties. The magnetic needle is violently agitated during its presence; streamers arrange themselves parallel to the magnetic meridian; and the corona is formed around that part of the heavens towards which the dipping needle spontaneously directs itself, that is, towards the pole of the dipping needle. In seeking an explanation of the aurora, general recourse has been had to electricity; but Professor Olmsted objected, that it cannot be accounted for from any of the known properties of electricity—that it is no explanation to call it "an electrical phenomenon"-that if electricity could satisfactorily account for the properties of the aurora, yet it does not account for its origin, which is the principal thing to be ex plained—and finally, that the atmosphere exhibits, during an aurora, no peculiar electrical excitement, and in the torrid zone, where electrical phenomena are the most remarkable, the aurora does not occur at all. After discussing, in a similar manner, all the existing hypotheses proposed to account for the aurora, the lecturer came to the conclusion, that they all fail to explain either its phenomena or its origin. He then urged the probability that its origin is extrinsic to the earth-that it is a "celestial visitant"-that the matter of the aurora is thrown into the atmosphere from some of those nebulous bodies that are known to be circulating in the solar system, one or more of which, in his opinion, produced meteoric showers. He did not think, however, that we are able to arrive at present at a full explanation of the origin of the aurora borealis, but holds that this is one of those points which are in reserve for the next or some future age. LECTURE IX. Meteoric Showers. The most remarkable display of shooting stars on record, occurred on the morning of November 13th, 1833. From a little after midnight to sunrise, the sky was lighted up with the most brilliant fire-works. The leading facts, when collected from various sources, and systematically arranged, proved to be as follows: The exhibition of shooting stars was seen in nearly equal magnificence and splendor all over North America, and it was chiefly confined to this country, having been witnessed on the east only about ten degrees from our coast, and on the west only a little farther than the confines of the Pacific Ocean; while, on the south, it fairly reached to the coast of South America. A great portion of the meteors were minute points which described a narrow streak of light in the air, appearing somewhat like snow driven furiously by the wind, and hence it was said to "snow fire;" but, at frequent intervals, much larger bodies descended along the arch of the sky, all seeming to proceed in lines, which, when traced back, came from one and the same point in the constellation Leo. At every return of the November shower since, the apparent "radiant," or place among the stars from which the meteors have appeared to emanate, has been likewise in the constellation Leo. In this, and in all the other November showers, the maximum, or period of greatest brilliancy, has occurred about four o'clock in the morning. Immediately after the occurrence of this great meteoric shower, it was ascertained that a similar one had occurred in 1799, on the morning of the 12th of November, arriving at its maximum at the same hour of the morning; and that, only one year previous, namely, the morning of November 13th, 1832, a like display of shooting stars was witnessed at Mocha, in Arabia. Subsequent investigations have established the fact, that the phenomenon has been exhibited in a greater or less degree on the 13th or 14th of November, every year since 1831, inclusive. In France, and other parts of Europe, in 1836, observations were made in a great number of observatories, which resulted in establishing a full conviction of the periodical return of the meteoric shower at this time of the year. Professor Olmsted remarked here, that it was no part of his theory of meteoric showers, that a shower should be exhibited every November. If it should occur at all, it would probably visit different parts of the earth in different years; but, according to his views of the origin of these showers, it is most probable that, like the aurora borealis, they have particular periods, which occur after long intervals, and last only a few years. Two other annual returns of the same phenomenon have been established,—one about the 10th of August, the other about the 7th of December. These showers, however, differ materially in several respects from those of November, and it is uncertain whether or not they depend on the same cause. The lecturer next examined several of the leading hypotheses which have been proposed to account for meteoric showers, such as that they are produced by electricity, by magnetism, by hydrogen gas collected in the upper regions, and by terrestrial comets revolving around the earth as ordinary comets do about the sun. All these suppositions he showed to be incapable of explaining the phenomena, or of accounting for the origin of these showers. LECTURE X. Cause of Meteoric Showers. Professor Olmsted began this lecture by stating the difficult inquiries involved in the investigation of the cause of Meteoric Showers. Such are the following: Was the origin of the meteors within the atmosphere or beyond it? From what height did they descend? In what direction? With what velocity? Of what size were the meteors ? Whence their light and heat? And, finally, whence their origin? In answer to these inquiries, it was shown, that the meteors came from a region beyond the atmosphere-that they came from an immense height, so great as not easily to be estimated by any data in our possession that they fell towards the earth in parallel lines, their apparent radiation from a common centre being the effect of propulsion -that they moved with an immense velocity, greater than could arise simply from the earth's gravity, which can never give to a body a greater velocity than seven miles per second-that some of the meteors were bodies of great size, often, at least, a large fraction of a mile in diameter—that they took fire and burned by falling into the atmosphere, and condensing the air before them so suddenly and so powerfully as to elicit from it the light and heat obscured. All these points were clearly proved by the most substantial reasons, which our limits will not permit us fully to recite. The professor finally instituted the inquiry, "What is the origin of these meteors?" The meteors were evidently composed of exceedingly light matter, else they would have come down to the earth-and of transparent matter, otherwise we should have seen them, at least by reflected light, before they entered the earth's atmosphere-and of combustible matter, since they were seen to burn. Now were these meteors all collected and restored to their situation in space, they would of themselves compose a body of great extent, and yet many reasons go to prove that they constitute but a small part of the body itself from which they are derived, being only the "extreme portions" of that body. Hence it is inferred, that the meteors fell to the earth from a large body in space, composed of such materials as the meteors themselves, and hence of a nebulous character, or analogous to the tails of comets. But the earth, in its revolution around the sun, had fallen in with this body for several successive years, in the same part of its orbit. Had the body remained there while the earth had gone round the sun? That is impossible, since no body in the solar system can remain at rest. If not attracted by some nearer body, it would descend immediately to the sun. This body, therefore, must have a revolution around the sun, in order to be found for several successive years in the same part of space. What is the period of its revolution? It must be either the same as that of the earth, or greater, or less. It could not be greater, for in that case it would not have got round so soon as the earth. It must therefore be either the same, or less. If less, the period must be some aliquot part of the earth's period, as one half, one third, etc., so as to perform just two or three revolutions while the earth performs one, otherwise the two bodies could not come together at the end of a year. Let us suppose, then, that the period of the meteoric body is one third of a year, or four months. Now when we know the time in which a body revolves around the sun, we can find the longer axis of its orbit by Kepler's law-that the squares of the periodic times of the planets are to one another as the cubes of the major ones of their orbits. This law is known to govern all the bodies of the solar system, and must govern the body in question. But were the period of this body only one third of a year, the greater axis of its orbit, as determined by the foregoing law, would not be sufficient to reach from the sun to the earth, and therefore a body revolving about the sun in such an orbit could never come so near the earth as this body actually did. Hence the period could not have been so small as one third of a year. Was it half a year? The determination of its orbit on this supposition, gives a major axis sufficient to permit the body to go around the sun, and still at its aphelion, or greatest distance from the sun, to come very near to the earth. Hence it is inferred, that the period must be either a year or half a year. Some reasons induce the belief that it is half a year; but this point is not yet fully decided. Since, then, a large nebulous or cometary body comes very near the earth about the 13th of November, ought it not to be seen by reflecting the light of the sun, even if it does not shine by its own light? There is a body of this description seen in the solar system, known by the name of the zodiacal light, exhibiting a faint pyramid of light, either after the evening or before the morning twilight. Does this body correspond, in its appearances and its different positions, with those which the body in question must assume? Professor Olmsted thinks there is much reason to believe that such is in fact the case, and that the zodiacal light itself is no other than a nebulous body revolving in the solar system, and coming at its aphelia very near to the earth. Still he does not consider this opinion respecting the zodiacal light as essential to the proof of the existence of such a meteoric body as that contemplated by the theory, but only as lending an incidental confirmation of it. He claims that all the conclusions respecting such a body are made out by a fair induction of facts, except what relates to its period of revolution. It is still uncertain whether that is a year or half a year. We may assume each of these periods, and compare it with the phenomena, and that which corresponds best to the facts will prove the true period. ART. V.-HISTORY AND LAW OF FIRE INSURANCE. FIRE insurance, though coming directly home to the interests and bosoms of a large portion of the community, is of modern origin, and is the offspring, in some degree, of crowded cities, and great accumulation of personal property. Though constituting but a small item in the lawmerchant, properly speaking, fire insurance, in amount of risks, has however in Great Britain, and we presume in this country, far outrun marine insurance; and the former has become, in some degree, to those whose habitations and whose interests are alone upon the land, what the latter is to those who do business upon the great deep. Still, though the risks have increased so much, the law in relation to fire insurance is neither abstruse nor complicated, and has not occupied much of the time or the talents of the judicial tribunals of the old or the new world. Founded upon contracts limiting and defining with much precision the extent and nature of the insurer's risk, the construction of these contracts has constituted generally the important point in most of the decisions upon this subject. When Mr. Park published his treatise on marine insurance in 1786, he says that he had been able to find but three leading cases upon fire insurance among the decisions of the English courts. Since then, however, fire insurance has greatly extended, and some new questions have arisen, and been discussed with a zeal and knowledge corresponding with the importance of the subject. The oldest fire insurance society or company now in existence, so far as we have been able to ascertain, is the Hand in Hand Contributionship Society of London, which was organized in 1696, about thirty years after the great fire with which that city was visited. It has been supposed that fire insurance societies had their origin in England soon after the fire, and the supposition is by no means improbable. When recurring to the condition of London at that period, we are led to feel that the afflictions of our city, severe as they are and have been, are light in comparison with those of that then ill-fated city. In the year 1665, the plague carried away nearly one hundred thousand of her inhabitants; and in the following year, the fire rendered houseless two hundred thousand more, and this with a population of little more than half a million. It was one of the consolations of the afflicted Londoners, that the fire had burned out the plague. Many of the narrow and filthy streets, where it had previously found a fit abiding place, were destroyed, and that scourge of London, so far as that city was concerned, might almost literally have been said to have been burned up. A brief recapitulation of the extent and consequences of that fire may not be uninteresting. It raged for three days, and burned over, within the walls of the city, three hundred and seventy-three acres, and about seventy-five acres without the walls. Thirteen thousand and two hundred houses were destroyed, embracing eighty-nine parish churches, besides chapels, together with the cathedral of St. Paul, and the Royal Exchange. It was checked by the blowing up of buildings with powder, but not until the inhabitants had almost given up in despair, feeling "That the strong man's arm was impotent to save, |