[Lesley. gQ [September. 



western angle, 8 miles from the First Ward, and 5 miles from the 

 Twentieth. 



The Fifteenth Ward station is on the western side of the triangle, 

 about 3 miles from the First Ward, 3 from the Twentieth, and 5 

 from the Twenty-second. Outside of a circle about 8 miles in radius, 

 the centre of which was nearly 2 miles north of the Twentieth Ward 

 station, at Ninth and Diamond Streets, the quantity of rain at this 

 time does not appear to have been such as to produce any noticeable 

 rise of the streams; but within these limits nearly all of the small 

 streams, including the Tacony on the north and the Cohocksink on 

 the south, were swollen beyond any freshet recorded concerning 

 them. 



Alono; the northern margin of the rain there was a remarkable 

 development of electrical disturbance, by which much damage was 

 done to several lines of telegraph wires and instruments. 



Prof. Henry added instances to show that it was a general 

 disturbance of the atmosphere, following the course and 

 obeying the laws of the more continuous storms later in the 

 season. 



Prof. Lesley described a curtain aurora which lie saw on 

 the 23d of July last, near Sydney, Cape Breton. 



The positive tone in which the possible nearness of auroral pheno- 

 mena to the earth's surface is denied by some physicists, makes it 

 desirable that every appearance to the contrary should be mentioned 

 and placed on record. Professor Potter, in Art. IX, Phil. Mag., 

 No. 158, page 51, reviewing a paper of De la Rive's in a preceding 

 number, pronounces his own hypothesis, — " that the aurorae boreales 

 are caused by the earth's electro-magnetism acting upon masses of 

 very rare vapors, of like constituents to the meteoric stones and va- 

 porous comets, moving in the planetary spaces under the laws of 

 gravitation, and coming near the boundaries of our atmosphere" 

 — <' the only tenable one." The lowest calculated locality of an ob- 

 served aurora, according to him, has been one given by Cavendish at 

 fifty-two miles. 



It seems unreasonable that the trigonometrical determinations of 

 Halley, Cavendish, Bergman, Dalton, and others, should despotically 

 exclude such observations as those recorded in No. XV of the Pro- 

 ceedings of the Literary and Philosophical Society of Liverpool, p. 104, 

 where Dr. Walker, Sir William Hooker, and General Sabine testify 

 that auroras are seen at so low a level that they interpose themselves 



