At 8h 52m, arch at the south growing fainter and breaking up. In a few minutes that quarter of the sky was nearly free from light. At 8:54 an imperfect corona formed at an altitude of 69°. At 8:56 a better one with bright wisp at its center, alt. 72°. At 8:58, corona 72° apparently in vertical plane cutting alpha Aquila. (Azimuth of the star then, by calculation, 8° 22' E.) The corona at these times not very definitely formed. At 9h 5m, a bright mass of light noticed in the east, irregular, expanding, and stretching obliquely upwards and towards the south. At 9h 10m this was met by a similar irregular mass of light stretching around simultaneously from the west, forming an imperfect band or arch, with very little light below it, its lower edge at this time having an altitude of 27° on the meridian. At 9h 12m its altitude was 20° 30', at 9h 23, 16° 15', and at 9h 31m, 16°, soon after which it faded. While this second curtain was shutting down in the south, it was noticed that the light in the north was rising gradually. At 9h 26m 30s its lower edge passed Polaris, and three minutes later was at an altitude of 62°, leaving the sky below nearly free from auroral light. At the same time, the phenomena overhead began to be more active and brilliant, streamers and cloudy masses of light of various hues, chiefly crimson, forming and vanishing about the corona, attaining a maximum of splendor from 36 to 43 minutes after 9, and at 49m having become comparatively faint. This magnificent umbrella-like canopy, first formed by these tinted streamers and flashes about 9h 33m, and then extending not more than 30° or 40° from the corona, with an irregularly scallopped or fringed margin, rapidly expanded in all directions, being more brilliant towards the north, and there presenting the appearance of a descending curtain, or rather succession of curtains, until at 9h 38m, it had shut down to the horizon all round, except in the south. The magnificence of the display at this time was not surpassed by anything in the brilliant Auroras of 1837, as remembered by the writer. The curtains just mentioned had at one time something of the drapery-like appearance characterizing the Auroras seen by the French commission at Bossekop in 1838-9. * Although the position of the corona is known to coincide in general with the direction of the dipping needle, its altitude was several times noted with a view to ascertaining its fluctuations, if any. The coronal point, however, was seldom or never sufficiently definite to make the observations of much value for this purpose. In addition to the notes of the coronas before 9 o'clock given above, the following were also made at the time. At 9h 15m 30s altitude of C. 73°, very definite. 9 18 bright streak or cloud above C. (alt. 76°) lasted 14m. At 9h 22m 9 24 9 26 9 28 alt. 73°, fine corona, long streamers. 30s" 68° 30', bright wisp near corona. C. not definite. 30 "73 15, 66 9 30 40 66 73 66 O, coronal cloud with rays from it. "74 30, very fine and definite. "75 15, C. not definite, colored streamers, splendid canopy. "72 45, tints brilliant. 66 74 0, C. definite, bright red, whole display magnificent. 66 74 0, splendid. "73 45, display much less brilliant. brilliant flashes and pulsations, chiefly towards corona. very little except in north. Flashes and pulsations continued with varying brilliancy until after 11 o'clock, and according to the testimony of others, the display continued through the night, at times with much splendor. The mean of the above altitudes of the corona is about 73° 20'. The dip at New Haven is about 73° 50'. A similar display of rosy streamers and waving light, though less brilliant, was witnessed on the morning of Sept. 2, after midnight, as noticed in one of the morning papers. It was observed about daybreak by Prof. Forrest Shepherd, whose attention was particularly attracted by the rapid flashes and pulsations overhead, which seemed to him to indicate a very low elevation of the phenomena above the earth. The display was continued on the evening of the same day, being most brilliant between 9 and 10 o'clock when the whole northern heavens to the zenith, and often beyond, was filled with upward flashes and pulsations here and there, chiefly of whitish light, and with but few streamers. On Sunday evening Sept. 4th, there were indications of a bright Aurora, though a clouded sky prevented it from being particularly observed. Auroral indications were also noticed on some other evenings of the preceding week. Unfortunately no magnetic observations were made at New Haven. The time piece used in noting the phenomena of the 28th was compared the same evening with the astronomical clock of the writer's observatory, and found to be only 5 seconds fast of N. H. mean time. SECOND SERIES, VOL. XXVIII, No. 84.-NOV., 1859. 4. Observations of Prof. ALEXANDER C. TWINING on the Aurora of Aug. 28th, 1859, made at West Point, New York, While the evening twilight was yet so strong as to make the phenomenon scarcely discernible, a rosy hue was seen spreading over a space reaching from the northeastern horizon to the north star and thence to my zenith, of uniform breadth throughout, and bounded south by a line through Alpha Lyrae, passing vertically down to the east. The time was 7b 25m by the watchwhich however varied six minutes from true local time (too fast it is believed, making the local time 7h 19m). In about ten minutes the southern boundary moved to Alpha Aquilae, and the rosy light had extended itself visibly over to the west, and streamers were seen in the northeast. Very soon the northern sky became variegated nearly up to the zenith with advancing bands and flakes of yellowish and reddish cloud with streamers intermixed. At a quarter before eight o'clock, by estimation of the true local time, the streamers in the north were numerous; and by careful observation they were perceived universally to move towards the west. At 8h 35m (by the watch) I looked again. A corona was then formed, and the auroral clouds and streamers were colored with tints of red and yellowish white. The most remarkable phenomenon was exhibited at the southern margin of the illumination. A yellowish cloud of extraordinary density and low altitude was seen advancing southward with an even and massive boundary which stretched entirely across the sky, in striking contrast with the clear blue beneath. It advanced beyond the bright star Antares, but soon receded and took a position which it retained ten or twelve minutes in a nearly level line exactly through that star, and a degree and a half, by estimation, below the star Epsilon Sagittarii, Its altitude therefore during that period-say from 8h 40m to 8h 50m (local time)—was about 111°, at the first named star, and about 11° at the last:-at the meridian it was, probably, 12°. This southern line gave an opportunity for comparative observations in different latitudes, which, if improved, will determine the height of that auroral cloud with an unparalled certainty and accuracy. There was also during this period another phenomenon equally remarkable and, if extensively observed in widely different latitudes, equally valuable. Ten or fifteen minutes before nine o'clock a bright spot formed at or near the meridian, and three or four degrees below the above named level margin. It soon became a long and narrow cloud-say 8° long and 21° broad at the middlebut pointed at its eastern and western extremities. It moved to the west in the clear sky, and parallel to the cloudy margin above it. In its course it passed centrally over the pair of bright contiguous stars in the end of the Scorpion's tail,-showing an altitude, at the cloud's middle line, of 7°. In two minutes as I estimated from subsequent recollection-it moved about forty degrees. It then was hidden by the mountains in the vicinity. Soon after this disappearance it was observed that the entire expanse of cloud in the south from the zenith down was making a similar progress west, at about the same rate, as nearly as could be estimated. At 8h 52m (local time) the original mass of vapor had moved nearly out of the southern field-leaving a far less dense and bright accumulation of cloudy strata over all that quarter. At twenty minutes to a quarter before ten o'clock I observed again. The corona was then finely formed by streamers thickly and completely developed on every side. In about three minutes the display became suddenly very gorgeous, the red and white (yellowish-white) streamers and banks being very brilliant. So they continued for a quarter of an hour at least. In this period pulsations or auroral waves were seen propagating themselves rapidly upwards, and quite to the corona. That these did move upwards was determined by a close scrutiny. The dome was completed on every side. The southern streamers were particularly observed to originate beneath in a line or arch which I roughly, and without express verification, judged to be at about the altitude of the cloudy margin as observed at a little before nine o'clock. It may have been somewhat higher. At ten o'clock, or a little earlier, the phenomenon of the narrow cloud moving westward was strikingly repeated. The cloud however in this instance was longer and less definite in shape. From ten o'clock to 12h 15m I did not observe. At this last mentioned time the auroral twilight shone brilliantly in the north, but my view in that quarter was obstructed. I observed again from 2h45m to 3h. The corona and dome were more regularly and completely formed than previously at ten o'clock, and more than I have seen them in either of the grand auroras of the last thirty years. The streamers were narrow, thick set, evenly distributed, and traceable to the corona. High in the north, observed against the constellation Cassiopeia, they moved across it from west to east, contrariwise to the motion in every instance I have before observed in any aurora. Yet my morning observations on this particular (and nearly or quite universal and yet generally unnoticed) phenomenon of transverse motion have not been so numerous as at evening.* At the spot * My conjecture as to the occasion of this remarkable feature of auroral phenomena has heretofore been the following: :-a streamer may be taken as the visible path of some portion of an electric current, normal, or nearly so, to the great thermal current of the earth. Such a normal current, in conformity with known laws, will experience a lateral movement under influence of the thermal current. It will also act upon the latter,-thus affecting magnetic intensity at the earth's surface, and, observed the motion was estimated as being fully 20° per minute. The ever varying wisps of cloud at the corona, and the southern streamers were also moving to the east. I left the display in full action without observing farther. The repetition which took place Sept. 3d, although on a vastly diminished scale of grandeur, I observed about one hour,―say from 9h to 10h P. M. It was remarkable for the character of the auroral waves, which passed upward, illuminating successively different definite spaces in their path. The motion of these waves was far more moderate than I have ever before remarked. In this instance I could not estimate it to exceed forty-five degrees of arc in a second of time. The movement was everywhere distinctly upward; but the determination of arcual or angular motion in this phenomenon, is excessively difficult and in exact. 5. Two letters from Prof. Daniel Kirkwood, Bloomington, Ind. [First letter.] TO THE EDITORS, &c. Aug. 29th, 1859. Gentlemen:The most extraordinary display of the Aurora Borealis I have ever witnessed was seen from this place last night. It was observed immediately after the close of twilight, and, in the course of an hour, the whole northern horizon from east to west was illuminated. The phenomenon continued from twilight to twilight; the brilliancy being greater at 4 o'clock this morning than at any previous hour. It was the lightest moonless night our citizens have ever known. Tints of various colors were seen in different parts of the heavens; but what struck spectators generally with wonder was a thin, gauzy cloud of brilliant red, which appeared first in the east about 9 o'clock in the evening, and which seemed to move almost horizontally till it reached the northwest; at 9h 30m lying precisely over the stars Alioth, Mizar and Benetnash, where it took the form of streamers, converging towards a point somewhat south of the zenith. At the same time an arch of light appeared, having one extremity in the horizon beneath, or rather westward of, almost of necessity the declination and dip; which seem to be merely resultants of all the electro-dynamic actions upon the needle, subsisting at the time. Under the above hypothesis, therefore, every development of streamers must ordinarily concur with three other phenomena, viz., a lateral movement of the streamers, a change of the needle's direction, and a change of magnetic intensity. The hypothesis of a magnetic property in the auroral medium-whatever the latter be-seems wholly gratuitous. It is only requisite that the medium, or substance through or along which the current passes, shall be susceptible of illumination by such passage. Certain phenomena however indicate that the current transports the auroral vapor laterally with itself. The importance of this class of observations to questions relating to the cause of the aurora, as well as to the direction of currents, is obvious. |