290 



[April 21, 



eye, and one of tlie spots is said to be tlie largest -which has appeared for 

 ten years. 



The theory is not improbable that sunspots are the result of solar elec- 

 trical or magnetic storms, and that auroras are the result of a disturbed 

 electrical condition of the earth, caused by induction from the sun. The 

 common cause for both phenomena is probably cosmical. 



Postscript.— Since this paper was presented, reports ot an unusual auroral dis- 

 play have come from all sections of the country. The aurora was visible across 

 the continent from the Atlantic to the Pacific coast. At San Francisco it Is re- 

 ported as the most brilliant seen for many years. A bright crimson light 

 appeared at 8.30 P. M., and the aurora showed various colors. At Omaha a crim- 

 son sheet across the sky Is described as its most remarkable feature. At Kansas 

 City it was said to be the finest aurora since 1873, and at 12.30 the whole northern 

 sky was lit up by streamers and red flames. At Warrenton, Mo., where it is 

 described as the most remarkable ever seen, the light was so brilliant that signs 

 i50 feet distant could be reai. A white arch of light, extending from east to 

 west, advanced southward at midnight to within SH degrees of the southern 

 horizon, and the corona was visible. At St. Louis it was seen early in the even- 

 ing, and it is stated that at 11 P. M. there was no electrical disturbance in the 

 telegraph wires. At Baltimore and Washington it was described as unusually 

 line, and consisting, first of a band of white light, later of shafts ot colored light 

 shooting through it, and afterwards of tremulous streamers moving with light- 

 ning rapidity, from north to south, while clouds of red Are hung in the north- 

 west. At Richmond, Va., it was seen distinctly at 3 A. M., and is reported as 

 the finest ever seen. At Boston, electrical disturbances were noticed shortly 

 alter the appearance of the aurora, and continued till late in tbe afternoon ot 

 the 17th. The wires from Boston to Albany and from Boston to New York were 

 worked without the battery, that to New York having been worked by the au- 

 roral current alone for three hours consecutively. 



In England, France, Belgium, Germany and Italy similar electrical perturba- 

 tions were observed. Upon the French telegraphic lines the perturbations wei"e 

 so frequent from April 16th to April 20th that special measures were taken by 

 the authorities to meet the contingency. Electrical equilibrium was restored 

 on the 21st. 



It is also of the greatest interest to learn that in England, where, so far as 

 known, no aurora was seen, tliere occurred a great magnetic storm at the precise 

 time that the aurora appeared in America. Mr. G. M. Whipple, ot the Kew Ob- 

 servatory, in a communication to Nature of April 20. says "a magnetic storm ot 

 unusual intensity raged from about midnight ot the 16th to midnight of the 

 17th," and that "a tremendous spot which appeared on the sun's disk on the 

 13th, is now rapidly approaching the central meridian, and a group observed on 

 Saturday in advance of it, has undergone considerable change in the interval." 



In Nature ot April 27th, he further reports that "the magnetic disturbance 

 began at 1L45 P. M. (6.45 P. M. Philadelphia time), April 16th, by an increase of 

 the declination, an augmentation of the horizontal force and a diminution ot 

 the vertical force. The movements of the declinometer became gradually more 

 rapid after 2 A. M. on the 17th (9 P. M. Philadelphia time), whilst its oscillations 

 extended farther and farther from its normal position, principally in the direc- 

 tion of increased westerly declination. From 4.30 to 9 A. M. (11.30 P. M. to 4 A. M. 

 Philadelphia time) the horizontal force had diminished so much that the trace 

 frequently passed off the paper, and the register was lost for a while. The min'- 

 mum of vertical foi-ce occurred at 5.55 A. M." (12.55 A. M. Philadelphia time). He 

 states that the disturbance did not die out till about 8 P. M. on the 17th. 



" During the 18th and 10th the magnets were unaffected, but at 3.45 A. M. of the 



