NATURAL SCIENCES OF PHILADELPHIA. 173 



The following gentlemen were elected membei's : 



Dr. John C. Spear, U. S. N. ; Jas. Lauman Harmar ; Dr. Fausto 

 E. Rendon. 



The following were elected Correspondents : 



Prof A. KoUiker, of Wurzburg, and N. H. Bishop. 



The Committee to which was referred the paper by Alphonzo 

 Wood, entitled " On Brevoortia," reported in favor of its publica- 

 tion in the Journal. 



On favorable report of the Committee, the following papers were 

 ordered to be published : 



The Auroral Display of April 15, 1869. 

 BY J. ENNIS. 



This auroral displaj was the brightest that has appeared at Philadelphia 

 eince the memorable one on the evening of August 28, 1859. On both these 

 occasions the light was most beautiful and striking, and during the iuterval 

 between the two no display occurred at all to be compared to these in bright- 

 ness, in beauty, in variety of coloring, and in general grandeur and magnifi- 

 cence of view. They both began just as the twilight was dying away. The 

 former slightly exceeded in gorgeous coloring, and the latter in duration, for 

 it continued to be still strikingly grand until after midnight. On both occa- 

 sions the chief colors were pale rose and pale green, but though pale in tint 

 they were very bright, clear and impressive. 



The cause of the aurora borealis is generally admitted to be the passage of 

 electricity from the northern region of the globe toward the south. This pass- 

 age I suppose to be constant, and in three different paths : the lower, 

 through the surface of the earth ; the middle, along the top of the atmosphere ; 

 and the higher, along what are called the magnetic curves ; the earth being 

 considered as a great magnet, with the poles north and south. 



The lower path becomes evident by studying the disturbances of the mag- 

 netic needle. Mr. Charles V. Walker came to the conclusion, from magnetic 

 irregularities, that over the south-eastern portion of the New England States 

 there is a stream of electricity of indefinite width drifting across the country, 

 moving to and fro in a line from N. 42 E. to S. 42 W.* Professor Loomis, of 

 Yale College, in discussing the great auroral display of 1859, says he found 

 similar magnetic disturbances over the continent of Europe, and that they are 

 propagated in a direction from N. 28 E. to S. 28 W. He intimates that per- 

 haps more observations would show the directions in Europe and America to 

 be the sanie.f Probably the electric currents on both continents would be 

 found floating more nearly north and south. All the facts of these magnetic 

 disturbances coincide with the idea that the electric stream is through the 

 earth's surface, the actual position of the magnets irregubirly deflected. 



The necessity for such a current through the earth's surface southwardly 

 becomes evident from the fact that the solid portion of the globe is constantly 

 robbing the atmosphere of its Electricity. We behold the tendency of this 

 fluid to come down in a thunder shower ; and sometimes, though rarely, the 

 thunder and lightning will fall from a cloud without any rain. I know an 

 instance, witnessed by several credible persons in the north-eastern part of 

 New Jersey, where a lightning stroke, with a loud report, and without anj- 

 rain, fell from a small summer cloud and struck one of the cattle in the field, 

 which had a bell at its neck. The solder of the bell was partly melted, and 

 the animal was killed. In all ordinary good weather, the higher we ascend 

 in the air the more strongly do we find it charged with electricity. The under 



* Amer. Journ. Sci. and Arts, vol. 32, p. 326. t Ibid, p. 334. 



1869.] 



