AUROKA BOREALIS. 



51 



appearing, after which the ordinary Aurora 

 Borealis was seen in the northern horizon. 

 As far southwest as Louisville, Ky., the aurora 

 made but little show, and its effects on the 

 telegraph wires were barely perceptible. Seen 

 from Indianapolis, the phenomenon was of a 

 whitish color, looking like clouds rent by the 

 winds. An hour later (at 9 o'clock) the sky 

 was illuminated first in the northwest, then 

 in the east, and streaked with spots of red 

 light which rapidly came and went. The dis- 

 play at that place lasted about an hour and a 

 half. In New York City and vicinity the 

 appearance of the phenomenon is accurately 

 given in the following, from an account fur- 

 nished by W. S. Gilman, Jr., to the American 

 Journal of Science for July. He was stationed 

 on the roof of Mr. Jacob Campbell's observa- 

 tory in Brooklyn, N. Y., a favorable position 

 for a good view. At 7i P. M., Mr. Gilman first 

 observed thin streaky clouds pointing upward 

 from the horizon, and evidently the beginning 

 of an auroral display. In a few minutes after- 

 ward the beams shot toward the zenith, and 

 the familiar auroral corona was formed. The 

 nucleus or apex of the aurora was seemingly a 

 cloud shaped like the internal area described 

 by a bow with the string drawn aside. The 

 southwest was clear, as it was generally dur- 

 ing the evening. From that point the wind 

 had been blowing all day. To the south the 

 auroral beams did not extend nearer the hori- 

 zon than Sirius, and at no time exhibited great 

 strength on the horizon. At 7 h 40 m rosy tints 

 appeared at different points of the compass, 

 those to the east and west of the zenith being 

 remarkably deep, and generally at an altitude 

 of 45 or more. At 8 p. M. the phenomenon 

 brightened after a brief dull period, and the 

 rose-tints were then very beautiful. Sulphur- 

 ous-yellow and greenish hues were also visible. 

 At 10 o'clock the aurora was faint, though 

 striking in its arrangement ; but at 10|- o'clock 

 the aurora reappeared with redoubled bril- 

 liancy, the nucleus of light being much larger 

 than it was earlier in the evening, and in shape 

 resembling the denser part of the great nebula 

 of Orion. At 2 A. M. when Mr. Gilman's ob- 

 servations ceased, only faint beams were per- 

 ceptible in the north, proceeding from the dark 

 segment along the horizon from K K E. to 

 K K "W. He regards this aurora as inferior 

 in brilliancy to one that he witnessed at Mount 

 Desert, Me., September 15, 1868, but possess- 

 ing more interest than the latter in the greater 

 grotesqueness of the clouds forming the coro- 

 na, and the rosy, greenish, and yellowish tints 

 assumed by the broad sheets of light which 

 streamed on all sides from the nucleus overhead. 



Mr. E. T. Kingston, connected with the Mag- 

 netic Observatory at Toronto, Canada, in a com- 

 munication to the same magazine, treats of the 

 aurora as seen at that place, in some of its 

 more scientific aspects. He says : 



A very grand exhibition of aurora, occupying more 

 or less the whole sky, took place on the night of 



April 15th, and continued, with but slight interrup- 

 tion, from dusk till daylight on the following morn- 

 ing. 



One part of the display, deserving notice from its 

 comparative rarity, was a dark segment similar to 

 those commonly seen in the north, though not so well 

 defined, which appeared about 9 p. M. in the south, 

 with an altitude of about 25. But the feature of still 

 more unusual occurrence consisted in a belt of lu- 

 minous haze from 5 to 10 in width, extending 

 through the zenith from the eastern to the western 

 point of the horizon, the material of which (in ap- 

 pearance) moved like a torrent from east to west with 

 prodigious velocity. 



The apparent movement of translation continued 

 from about 13 h 10 to 13 h 50 m , when .the matter com- 

 posing the belt became affected by pulsations, which 

 succeeded each other in the order from east to west, 

 and with a rapidity still greater than that of the pre- 

 vious apparent motion of translation. 



About 14 h the belt broke up and the pulsations 

 became visible over the whole sky, the order of their 

 succession being from the horizon to the zenith. At 

 15 h the pulsations became intermittent, and ceased 

 to maintain any apparent order in the their occur- 

 rence : they gradually became more feeble and ceased 

 with daybreak:. 



Throughout the night a generally diffused lumi- 

 nosity prevailed, such as is commonly seen with a full 

 moon and hazy sky. This was evidently not occa- 

 sioned by the moon, which was scarcely four days 

 old, and Avas low in the horizon, "but was part of the 

 aurora itself, the brilliancy of whose more active fea- 

 tures it greatly impaired. 



Throughout the day and night a considerable mag- 

 netic disturbance was going on. 



Declination. As regards the declination, the aver- 

 age deviation was 15' of arc, or three times the limit 

 required to entitle a disturbance to be considered as 

 large. The easterly deviations were the more nu- 

 merous, but the westerly were on the average fifty 

 per cent, greater in extent. 



The greatest easterly deviation was 93' at 3 p. M., 

 and the greatest westerly deviation 85' at T h 15 m p. M. 



The deviations after midnight were nearly all east- 

 erly. 



Total Force. The disturbances of the total force 

 were on the average nearly seven times what may be 

 designated as the inferior limit of a disturbance, or 

 .0004 of the total force. 



The number of the disturbances which increased, 

 and of those which diminished the force, were nearly 

 equal ; but the average magnitude of the latter was 

 to that of the former in the ratio of 8 to 5. 



The greatest disturbance which increased the force 

 was 11 (the unit being .0004), and occurred at 5 h 15 m 

 p. M., while the greatest disturbance diminishing the 

 force was 23, and occurred at 8 P. M. 



The disturbances which diminished the force nearly 

 all took place between 6.30 p. M. and midnight. 



Inclination or Dip. The disturbances of the dip 

 had an average value of about 15', or 15 times the 

 disturbance limit. 



The disturbances which increased the dip were the 

 more numerous, but those which diminished the dip 

 were of nearly twice their magnitude. The greatest 

 increase of dip was 35, and occurred at 10 h 30 ra p. M. , 

 and the greatest diminution of dip was 64', and oc- 

 curred at 3 P. M. 



The disturbances increasing the clip nearly all took 

 place after 7 P. M., those that diminished the dip hav- 

 ing^ occurred during the day. 



On the whole, the aurora, together with the mag- 

 netic disturbance which preceded and accompanied 

 itj was more remarkable than any that have been 

 witnessed at Toronto since September, 1859. 



J. A. Angstrom sends to Poggendorff's An- 

 nalen a report of his spectroscopic studies of 

 the aurora. He says that, in the winter of 



