alone was absent. The measurements are exact to half a d of the scale. To determine the approximate wave-lengths of these lines parison was made both with certain elemental lines and wit lines of the solar spectrum. On the scale of this instrumen elemental lines employed read as follows: Ka 63, Lia 79, Srß 80, H(c) 82, Caa 91, Sra 96, Caß 113, H() The Fraunhofer lines measured as follows:- a 70.5, B 76, C 82, D 100, E 124-5, b 130, F 146-5, G 189. Direct interpolation was used in comparing the wave-length the auroral lines with those given above, the wave-lengths of Fraunhofer and elemental lines being taken from Gibbs's ta (this Journal, II, xliii, 1; xlvii, 194). This method was belie capable of giving results as close as the instrumental meast ments. In this way the wave-lengths of the five auroral h1were obtained as given in the following table:→ In this table, column 1 gives the auroral and the Fraunhofer lines: column 2, the number of these as measured upon the scale of the spectroscope used; column 3, the wave-lengths of these lines o tained as above stated; column 4, the wave-lengths of the aurora. lines, given by themselves; and column 5, the wave-lengths of what I assume to be the same lines, with their wave-lengths s measured by the observers mentioned. The point of particular interest in this observation is the fact that the line (4) of wave-length 502 is not laid down in any author ity accessible to me as having been observed in the auroral spectrum. Indeed, no previous observer, so far as I know, has seen any auroral line between the Fraunhofer lines b and F. Professor C. A. Young (this Journal, III, ii, 332, Nov., 1871) gives two lines -Nos. 56 and 57, or 1866-8 and 1870-3 of Kirchhoff-observed by him in the sun's chromosphere and also by Rayet in the eclipse of 1868, one of which may coincide with this fourth auroral line. New Haven, Nov. 13, 1871. [NOTE.-Since the above was in type, the Astronomische Nachhten for October 24th, No. 1864, has been received. It conns a notice of auroral spectra as observed at the Bothkamp servatory by H. Vogel, which is dated August, 1871. In ordiry auroras 6 lines were seen, in the red streamers 7. The folving are the wave-lengths given: 629.7 556.9 538.2 523.3 518.9 500.3 Very bright line. Brightest line of the spectrum. Markedly weaker when the red line is also present. Very faint line. (Doubtful.) Pretty bright line. Very bright when the red line is present. At other times, as bright as the last. Pretty bright line. om 469-4 S Broad band, brighter in the center. Very weak in { the red streamers. e line of wave-length 500-3 is apparently the same observed by , and given as 502. Vogel thinks he has obtained evidence in support of the assumpn that the auroral spectrum is an air spectrum, modified by ditions of pressure and temperature. The whole number of lines which have been seen and measured he spectrum of the aurora by different observers appears to be as follows: Many other observations of auroral spectra have been made, c in most cases the lines were not measured even approximately. G. F. E 2. An Explosion on the Sun; by C. A. YOUNG. (Boston Jer nal of Chemistry).-On the 7th of September, between half p twelve and two P. M., there occurred an outburst of solar energ remarkable for its suddenness and violence. Just at noon t writer had been examining with the telespectroscope* an enorm protuberance of hydrogen cloud on the eastern limb of the sun It had remained with very little change since the preceding noon-a long, low, quiet-looking cloud, not very dense or brillian nor in any way remarkable except for its size. It was made: mostly of filaments nearly horizontal, and floated above the chrmospheret with its lower surface at a height of some 15,000 mile but was connected to it, as is usually the case, by three or fou vertical columns brighter and more active than the rest. Lockye compares such masses to a banyan grove. In length it measure 3' 45", and in elevation about 2 to its upper surface-that is, sinc at the sun's distance 1" equals 450 miles nearly, it was abor 100,000 miles long by 54,000 high. At 12h 30m, when I was called away for a few minutes, there was no indication of what was about to happen, except that one of the connecting stems at the southern extremity of the cloud had grown considerably brighter, and was curiously bent to one side and near the base of another at the northern end a little brillia lump had developed itself, shaped much like a summer thunder head. Figure 1 represents the prominence at this time, a being the little "thunder-head." What was my surprise, then, on returning in less than half s hour (at 12h 55m), to find that in the meantime the whole thing had been literally blown to shreds by some inconceivable up-rush from *This is the name given by Schellen to the combination of astronomical tel scope and spectroscope. The chromosphere (called also sierra by Proctor and others) is the layer hydrogen and other gases which surrounds the sun to a depth of about 7,0 miles. Of this the prominences are mere extensions. The sketches do not pretend to accuracy of detail, except the 4th; the th rolls in that are nearly exact. eneath. In place of the quiet cloud I had left, the air, if I ay use the expression, was filled with flying débris-a mass of etached vertical fusiform filaments, each from 10" to 30" long by or 3" wide, brighter and closer together where the pillars had rmerly stood, and rapidly ascending. When I first looked some of them had already reached a height nearly 4' (100,000 miles), and while I watched them they rose ith a motion almost perceptible to the eye, until in ten minutes h05m) the uppermost were more than 200,000 miles above the lar surface. This was ascertained by careful measurement; the ean of three closely accordant determinations gave 7' 49" as the treme altitude attained, and I am particular in the statement ecause, so far as I know, chromospheric matter (red-hydrogen in is case) has never before been observed at an altitude exceeding The velocity of ascent also, 166 miles per second, is considerly greater than anything hitherto recorded. A general idea of 3 appearance, when the filaments attained their greatest elevation, ay be obtained from figure 2. As the filaments rose they gradually faded away like a dissolving oud, and at 1h 15m only a few filmy wisps, with some brighter 2. streamers low down near the chromosphere, remained to mark the place. But in the meanwhile the little "thunder-head," before alluded to, had grown and developed wonderfully into a mass of rolling and everchanging flame, to speak according to appearances. First it was crowded down, as it were, along the solar surface; later it rose almost pyramidally 50,000 miles in height; then its summit was drawn out into long filaments and threads which were most curiously rolled backward and downward, like the volutes of an Ionic capital; and finally it faded away, and by 2h 30m had vanished like the other. Figures 3 and 4 show it in its full development; the former hav been sketched at 1h 40m, and the latter at 1" 55". The whole phenomenon suggested most forcibly the idea of an blosion under the great prominence, acting mainly upward, but o in all directions outward, and then after an interval followed a corresponding in-rush: and it seems far from impossible that the mysterious coronal streamers, if they turn out to be t solar, as now seems likely, may find their origin and explanati in such events. 3. The same afternoon a portion of the chromosphere on the opp site (western) limb of the sun was for several hours in a state d unusual brilliance and excitement, and showed in the spectrum more than 120 bright lines whose position was determined and catalogued, all that I had ever seen before, and some 15 or besides. Whether the fine aurora borealis which succeeded in the evering was really the earth's response to this magnificent outburst of the sun is perhaps uncertain, but the coincidence is at least sug gestive, and may easily become something more if, as I somewha: confidently expect to learn, the Greenwich magnetic record indi cates a disturbance precisely simultaneous with the solar explosion Dartmouth College, September, 1871. 3. November Meteors in 1871.-On the night of November 13th-14th, the writer, with Prof. Lyman and about two others watched for meteors from 11h 20m onward, with the following re sults:: Between 11h 20m and 11h 30m we saw 9 meteors. Sky obscured 30 66 45 66 8 66 Fewer clouds, Shortly after 1h 45m the clouds had entirely closed over, and did not break away afterward. A very few of the 98 meteors seen were of the November meteor system, not more, we judged, than of the number seen. We were therefore at the time of the watch not in the meteor stream. If the earth passed through it this year, it did so earlier than 11 20", or later than 1 20", of the night of the 13th-14th. H. A. N. |