124 AURORA BOREALIS AURUNGABAD interrupted by the fields of ice. The study of the aurora with the spectroscope hus revealed some important facts, though it has as yet thrown no light on the nature of the phe- nomenon. Angstrom of Sweden, in the winter of 1867-'8, recognized the existence of a bright yellow-green line in the auroral spec- trum ; and Otto Struve of Russia presently confirmed this result. It was at the time sup- posed that this line constituted the whole of the spectrum ; and Dr. Huggins, commenting on the discovery, remarked in 1868 that the result seemed surprising when the ordinarily ruddy hue of the aurora was taken into ac- count. " But Gen. Sabine tells me," he adds, " that in his polar expeditions he lias frequently seen the aurora tinged with green, and this appearance corresponds with the position of the line seen by M. Struve." Later observa- tions, however, and especially those made by Prof. Winlock in this country, have shown that the auroral spectrum is far more complex than had been supposed, and that it is also variable. It would appear that the bright green line is always present, and that it is nearly always the brightest line of the spec- trum. But there is also a band in the red which, though usually much less intense, yet becomes even brighter than the yellow-green line when the red streamers of the aurora are exceptionally brilliant. The wave lengths of the green and red light correspond respectively to 558 and 635. Besides these there are faint greenish and bluish lines corresponding to wave lengths 544, 531, 522, 518, 501, and 485. Two other bands in the blue and violet between the lines F and G (one of them very close to G) have been detected in the spectrum of white parts of the aurora. They disappear or be- come faint in the parts having an intense red tint. During the great auroral display of Feb. 4, 1872, Father Perry of the Stonyhurst ob- servatory (England) remarked that " the green line could always be detected, even where the unassisted eye failed to notice any trace of auroral light. This," he adds, " might sug- gest the advisability of a daily observation with a small hand spectroscope for those who are desirous of forming a complete list of auroral phenomena. Magnetic disturbances are a sure guide in the case of grand manifesta- tions of aurora ; but might not a very slight aurora be observable without the magnetic needle being sensibly affected ? " One of the most remarkable circumstances hitherto ascer- tained respecting the aurora is the partial agreement of its spectrum with that of the solar corona. It is not indeed the case, as is sometimes stated, that the principal line in the coronal spectrum (known as the 1474 line, be- cause agreeing with the corresponding line of KirchhofFs scale) coincides with the bright yellow-green auroral line ; but another and fainter auroral line agrees with Kirchhoff s 1474, and there is sufficient general resemblance be- tween the coronal and auroral spectra to justify the theory that a real resemblance exists between the aurora and the solar corona. This theory was first worked out and published by Prof. W. A. Norton of Yale college ; but Prof. Winlock of Cambridge also formed and published a similar theory. Some doubt seems still to prevail on the question whether the bright green line of the auroral spectrum be- longs also to the spectrum of the zodiacal light. Angstrom and Respighi have asserted that this is the case ; but others deny that the auroral green line is ever seen in the zodiacal spectrum save when an aurora is in progress. Mr. Webb observes of the zodiacal light, Feb. 2, 1872 : " It seemed to show a ruddy tinge not unlike the commencement of a crimson aurora borealis ; this may have been a decep- tion, but it was certainly redder or yellower than the galaxy. At 7 I examined it with a pocket spectroscope which shows very dis- tinctly the greenish band of the aurora ; but nothing of the kind was visible, nor could any- thing be traced beyond a slight increase of general light, which in closing the slit was ex- tinguished long before the auroral band would have become imperceptible." M. Liais also, who has for several years studied the zodiacal light in tropical countries, finds its spectrum to be ordinarily continuous. Yet undoubtedly the yellow-green line is seen in the spectrum received from the region occupied by the zodi- acal, during auroral displays; though whether it is then simply the auroral line seen in the direction of the zodiacal as well as in others, or partly received from the zodiacal itself, re- mains an open question. In the latter case it would follow, of course, that there is an intimate connection, as Mairan long ago suspected, between the zodiacal light, which is undoubt- edly a cosmical phenomenon, and the aurora, which is as undoubtedly a terrestrial manifesta- tion, though not improbably of cosmical origin. Prof. Olmsted had several years ago assigned to the aurora an interplanetary origin. " The nebulous matter," he reasoned, "like that which furnishes the material of the meteoric showers or the zodiacal light, and is known to exist in the interplanetary spaces, is probably the cause of the auroral displays. The peri- odical return of the phenomena indicates such a position ; so too its rapid motion, which ex- ceeds that of light or electricity, and the ex- tent of surface over which the phenomenon is seen at the same time." It should be added that during the months of January, February, and March, 1872, when auroras occurred with unusual frequency, the zodiacal light shone with exceptional brilliancy. AURUNGABAD, a city of western Hindostan, in the native state of Hyderabad or the terri- tory of the Nizam, on the Doodna, a small tributary of the Godavery, 175 m. E. N. E. of Bombay. It was an unimportant village called Gurka until the time of Aurungzebe, who made it a favorite residence, and built here a mausoleum to the memory of his daugh-
