NATURAL PHILOSOPHY. 117 



in this class of operations, especially when more than one charge has 

 to be fired, on account, firstly, of the increased difficulty in thor- 

 oughly insulating the conducting wire and the necessary connection ; 

 and, secondly, because of the flowing in of the water upon the bared 

 poles immediately after one or two in the series were ignited, thus, 

 by completing the circuit, preventing the explosion of the rest. The 

 charge of powder was enclosed either in a tin canister or a Mackin- 

 tosh bag, with a fuse in the midst, and connection established with 

 the insulated wire on the one hand, whilst the other pole was placed 

 in communication with the metal of the canister, or brought out into 

 the water in the case of the vulcanized India-rubber bag. 



THE AURORA OF SEPT. 2, 1859. 



Professor Looniis thus locates the geographical position of the cele- 

 brated aurora of Sept. 2d, 1859 : 



It formed a belt of light encircling the northern hemisphere, ex- 

 tending southward in North America to lat. 22^, and reaching to 

 an unknown distance on the north ; and it pervaded the entire inter- 

 val between the elevations of fifty and five hundred miles above the 

 earth's surface. This illumination consisted chiefly of luminous beams 

 or columns, everywhere parallel to the direction of a magnetic needle 

 when freely suspended ; that is, in- the United States these beams 

 were nearly vertical, their upper extremities being inclined south- 

 ward at angles varying from 15 to 30. These beams were, there- 

 fore, five hundred miles in length, and their diameters varied from 



* ^j ' 



five to ten and twenty miles, and perhaps sometimes they were still 

 greater. 



These beams were simply illumined spaces, and the illumination 

 was produced by a flow of electricity. That this illumination was 

 produced by electricity is proved by the observations of the mag- 

 netic telegraph. During these auroral displays, there were devel- 

 oped on the telegraph wires electric currents of sufficient power to 

 serve as a substitute for the ordinary voltaic battery. That the 

 agent thus excited upon the telegraph wires was indeed electricity, 

 is abundantly proved. 



Professor Loomis also states that it appears from the result of his 

 observations that the remarkable auroral display which prevailed 

 throughout a large portion of the northern hemisphere from Aug. 

 28th to Sept. 4th, 1859, was accompanied by a display about equally 

 remarkable in the southern hemisphere ; and the periods of greatest 

 brilliancy were nearly contemporaneous in both hemispheres. It also 

 appears, from examining the records of the British Magnetic Observ- 

 atory at Hobarton, in Van Dieman's Land, running through a series 

 of years, that every tune that an aurora has been seen in the horizon 

 of Hobarton an aurora has appeared the same day in the northern 

 hemisphere, or at least such extraordinary perturbations were ob- 

 served as are almost certain indications of the presence of an aurora 

 in positions more or less distant. If the number of these coincidences 

 were not as yet too few, we should naturally be led to admit that an 

 extraordinary aurora in the southern hemisphere is always accom- 

 panied by one in the northern ; in the same way as all the causes 



