storms. It is well known by experiments with the electrical doubler,* that almost all bodies possess a certain degree of electrization, which is variable from a considerable number of circumstances. It is also known from Franklin's experiments of the can and chain, as well as from numerous other facts, that the intensity of the electric state will be augmented by diminishing the surfaces of bodies. In this way, as well as from other causes, it is inferred that clouds become highly electrified during the progress of their condensation; so that flashes of lightning pass between them and the earth, and between each other. From other observations and deductions, it has been also rendered highly probable that the long range of clouds in a storm of this nature does serve as a conductor, through which flashes of electric fire are conveyed from one part of the earth to another part in a different state. The facts above described seem uncommon, and, if collated with other more usual events, may afford some instruction concerning this class of phenomena. I do not highly esteem the conjectures which present themselves to me on this occasion; but shall communicate them, because they tend to point out future objects of research. The singularity of this thunder storm appears to have arisen from the mass of aqueous vapour having been much too small to afford a favourable communication between the two opposite states of electricity on the surface of the earth. If the mass of clouds be supposed to have been at first near the eastern portion of the earth, and to have become electrified and repelled, they would, on the common principle of bodies in that state, be repelled, and pass swiftly to the western part of the surface to deposit their electricity, as soon as they came within the striking distance. In this situation, it may be imagined that the supply or communication might continue to be made by the eastern part of the cloud acting in the manner of a point, while the western part emitted flashes; a supposition which is rendered more probable by the consideration that most thunder clouds are ragged or pointed on one side, and round or swelled on the other; and also that the disposition of any conductor to receive electricity without explosion is much greater than to give silently, even when the terminations are alike. I conjecture, therefore, that the lightning came from the east, and passed through the clouds to the west; that the posterior extremities of the clouds were illuminated as points usually are; that the electric motion of these low clouds at first caused an easterly wind; that some change in the general state of electricity, or perhaps the mere exhausted state of the clouds, caused them to pass rapidly back to the original reservoir, as in the most common experiments of electricity; that this return produced first a strong eddy in the lower air, which threw up the dust, and afterwards a contrary stream of wind, by which the rain was beaten against the west front of the house. But why the • "New Experiments on Electricity." By the Rev. A. Bennet, F.R.S., 8vo, London. clouds should have been illuminated with a red colour during their western course, and afterwards with blue, does not seem deducible from any facts I know of. It may perhaps be analogous to the colours of the aurora borealis. The contrary lower current, when the clouds were removing to the north, seems to have been a natural consequence of their remoteness. It is probable that the returning current of the air, which must have been driven before the mass of clouds when they were moving very near the earth, took place entirely in the upper part of the air, where, in that case, there was more room. On an Aurora Borealis seen at Woolwich, December, 22, 1834. By WILLIAM STURGEON. A BEAUTIFUL aurora borealis was seen from this place last night. I was on Woolwich Common when I first saw it, then exactly six o'clock. It consisted of several groups of vertical beams of pale yellowish light on both sides of the north star, extending nearly to equal distances on the western and eastern directions. These beams presented the strongest light at their bases, and grew gradually fainter, to their superior extremities, where they softened and gently glided into the most attenuated light, and were lost at various altitudes, some of which were near to the zenith. These streamers soon faded, and gave place to a few straggling vertical corruscations, displayed in various parts of the northern sky, which in their turn were again succeeded by the finest streamers I ever beheld. It was now five minutes past six. These splendid streamers were of the same tint as the former, and extended from the black nucleus near the horizon to the zenith in nearly the same manner; but the refulgence of these far exceeded that of the former. These streamers consisted principally of two parallel groups, one on each side of the north, and with some considerable distance between them. Smaller streamers were, however, playing in the intermediate space and also on their outer horizontal skirts. The horizontal boundaries of the aurora, at this time, seemed to be the Milky Way on the west, and near to the planet Mars on the east. From this time the aurora gradually diminished in splendour, and about seven was nearly lost; it occasionally, however, brightened with a few faint flashing momentary streamers till between ten and eleven, at which time I discontinued my observations. During the display of the fine streamers, which first presented themselves about five minutes past six, I hurried home to adjust a magnetic needle. It was about half-past six before I had my magnetic apparatus fit for observation, and the splendour of the aurora had now passed its meridian. I diligently watched the needle and the aurora till half-past ten, but observed nothing in the motions of the former that could possibly be attributed to the influence of the latter. From the brilliancy of the aurora at six o'clock, I imagine that it was exhibited at a much earlier period of the evening, but I have had no opportunity of ascertaining the fact from persons likely to have seen it. I think it is likely that the aurora was very fine in Scotland, and perhaps in higher north latitudes, after seven o'clock, perhaps till nine or ten. Artillery Place, Woolwich, Dec. 23, 1834. W. STURGEON. P.S. This aurora appeared to have no particular respect for the magnetic north: it was nearly, if not exactly bisected by the true meridian during the whole of the time I observed it. Description of the Aurora Borealis of November 16, 1835, AN aurora borealis of a very unusual character was seen in this neighbourhood, and I imagine over a large tract of country, on Wednesday evening the 16th instant. I was walking from Greenwich to Woolwich, between nine and ten o'clock, and when I had arrived at the top of Maize Hill, by the side of Greenwich Park, then about ten minutes past nine, my attention was first attracted by the fine light of the aurora in the north. I walked on a little further till a good opening to the northern horzion presented itself from the road leading from Maize Hill to Mr. Angerstein's estate. At this opening I made a determined stand, for the purpose of observing any novel phenomenon which the aurora might happen to present. At this time it consisted principally of a very extensive lateral range, on both sides of the pole star, of vertical streamers, which were pencilling the northern heavens from about 15° above the horizon to Cassiopeia's Chair, then about the meridian; and so uniform was their arrangement and splendour, that they presented one sheet of yellowish white light, the most intense at the base, and becoming more and more faint as they proceeded upwards, until quite lost at their terminal altitudes. This appearance of the aurora had but just stamped its impression on my mind, when in one moment the whole of the northern heavens appeared in one complete state of undulating commotion, heaving upwards in rapid succession immense waves of light,* which, like the streamers which preceded them, gradually diminished in These waves were seen at Milton, next Gravesend, by my scientific friend Mr. Swinny; and I beg to acknowledge the obligation I am placed under to Mrs. Swinny, who also saw these waves, for a more happy description of them than any I had before thought of. They appeared to this lady as" waves of thin smoke or steam, behind which was placed a strong light." A more expressive description could not possibly be given. brilliancy from their source near to the horizon till their arrival at the zenith, which was their general vanishing point. The horizontal range of the aurora during this unusual display, was eastward as far as Jupiter, whose azimuth from the north was then about 75°; and perhaps about the same extent westward on the other side of the pole star. I observed it stretch to beyond a Lyræ (Vega), whose azimuth from the north was about 60°, but could not very well ascertain the position of the western extremity at the place where I was standing, on account of the reflexion of the gas light in London mixing with that of the aurora, and the intervention of trees, &c. This extensive ocean of light, which illuminated nearly half of the visible heavens, and whose waves rolled with the rapidity of thought, lasted about eight or ten minutes, perhaps longer, when they gradually began to disappear, and the aurora to contract in all its dimensions. Until this time (nearly half-past nine) no dense nucleus had marked the centre of the aurora: the stars were seen between the horizon and the luminous base as decidedly, though not so clear, as if no aurora were present. The star Benetnasch, in the the tip of the tail of the Great Bear ( Ursa Majoris), was one of those which were observed below the aurora; but Mizar (Ursæ Majoris), then on the meridian below the pole, was seen in the bright arched base of the streamers and waves. The last-mentioned change in the appearance of the aurora brought it gradually to that state which is usually exhibited in some period or another of this boreal phænomenon. The dense black nucleus began to form, and soon curtained the stars which had previously twinkled in that segment of the northern sky. The luminous margin also, its usual attendant, became well defined, and its highest point was well marked to the westward of the meridian, perhaps nearly in the magnetic north. I now walked on, keeping the aurora in view, which shot occasional streamers from various parts of the luminous arch. Just before I entered Woolwich, about ten o'clock, another fine display of vertical streamers spread over the northern sky, and continned for nearly a quarter of an hour. By this time 1 reached home; but too late to ascertain their effect, if any, upon the magnetic needle, for they faded away very rapidly after my arrival, and before eleven the aurora had entirely disappeared. During my walk home, I observed several fine meteoric stars, most of which appeared to be shot from the same point of the heavens, which point was somewhere in a right line between me and the Twins. One of these meteors shot with a moderate velocity across the north part of the meridian, at an altitude of about 80°, and appeared to traverse an arch of the heavens of 90° or 100°. It burst into several luminous fragments at the western termination of its range, and became extinct in a moment. I listened for some time, but heard no noise, neither did my servant who was with me, and who listened attentively at my request. I had previously pointed out to him the direction he was to look in, and he saw the meteor from the first to its last appearance. He also directly afterwards saw another from the same quarter, which traversed the heavens in nearly the same direction as the former. He called out to me, but it was lost without my seeing it. These meteors was seen above five minutes before the last display of streamers mentioned above. I saw no appearance of the aurora to the south of the zenith, though frequently looked for. The sky was quite clear of clouds, and the black southern expanse, studded with its brilliant stars, afforded a fine contrast to the display of the aurora in the north. Artillery Place, Woolwich, Nov. 19, 1835. N.B. Whilst writing the above, a friend has called on me, who saw fine streamers about half-past eight o'clock. On Electro-pulsations and Electro-momentum. It is very well known to the readers of the "Philosophical Magazine,” that I have long considered electric currents, when transmitted through inferior conductors between the poles of a voltaic battery, as the effect of a series of distinct discharges, in such rapid succession as not to be individually distinguished by the senses. Such currents I have called electro-pulsatory. See my theory of magnetic electricity in the "London and Edinburgh Philosophical Magazine," vol. ii, p. 202. By following up these views of electro-pulsations, I was about two years ago enabled to dispense with all acid or saline liquids, in the employment of galvanic batteries for the purpose of galvanizing, as it called, either to satisfy the curiosity or as a medical process; and my plan, which answers very well, I have found to be productive of a considerable saving in the expense necessarily attendant on the use of voltaic batteries when excited by acid solutions. It is well known that a Cruikshank battery of about a hundred pairs will, by employing water alone in the cells, charge to a certain degree of intensity almost any extent of coated surface of glass that we please; and that the same degree of charge is given to it by a single contact of the conductors, however short its duration. This being understood, and understanding also that the shock produced by any discharge from a given intensity would be proportional to the quantity of fluid transmitted in a given time, it was easy to foresee that a series of shocks in rapid succession might be produced by some mechanical contrivance, and that the degree of force might be regulated by varying the extent of coated surface. My first experiments were made with a hundred and fifty pairs of three-inch plates, and about seven feet on each side of coated glass; and my apparatus for producing a rapid succession of shocks was one of Mr. Barlow's stellated electro-magnetic wheels which was soldered to an iron spindle and put into rotatory motion by a |