130 Transactions. — Miscellaneous. 



tion on ihe Peak of Teneriffe, Piazzi Smith found the desic- 

 cating power of the atmosphere such that the ink he used in 

 writing would often dry in the pen during its passage from the 

 inkstand to the paper; and those of his instrument -boxes 

 which were fastened with ghie came in pieces, from the 

 moisture necessary to its Irolding-power being dried out of 

 the ghie, and the ghie converted into powder. 



That dry air is a non-conductor of electricity was proved fifty 

 years ago at an exhibition in what was called the Adelaide 

 Gallery, in London, where the discharge of the electricity 

 stored in an enormous Leyden jar through a column of dry 

 air in a glass tube caused it to pass as a ball of white light, 

 occupying an appreciable time in its passage ; while a similar 

 discharge through a similar tube from which the air had been 

 withdrawn poured as a stream of purplish light. This proves 

 that dry air offers, jnv tanto, obstruction to the passage of 

 electricity, which the absence of air freely permitted. Dry air, 

 being a non-conductor of electricity, must, in the same way as 

 glass, sealing-wax, and dry brown paper — non-conductors of 

 electricity — be a good electric, and, subjected to appropriate 

 conditions, generate electricity. 



Faraday demonstrated that oxygen gas is magnetic — that 

 is, acted upon by electricity it acquired polarity in the same 

 sense as steel does. 



This cushion of electric matter carried round the earth in 

 its diurnal revolution cuts the lines of physical force which 

 hold the earth in its place toward the sun while travelling 

 through space at rates varying from a thousand miles an hour 

 to nothing. That a process analogous to friction must be 

 the result is a reasonable conclusion, deriving confirmation 

 from the existence of the trade- winds and the Gulf Stream. 

 That the earth's atmosphere, revolving at such speed, and 

 exposed to the action of those actively-acting lines of physical 

 force, could be so exposed without a physical effect being pro- 

 duced, is a conclusion which I cannot believe. 



This effect upon the dry atmosphere is the generation of 

 electricity, which, acting upon its oxygen, gives magnetic 

 force directly to so much of the oxygen as is directly subject 

 to the electrical action, and by induction to any not so sub- 

 ject. And thus is constituted the hollow sphere to which are 

 due the phenomena of terrestrial magnetism. 



The view here put forward is confirmed by the coincidence 

 observed between the appearances of spots on the sun and 

 those of the aurora borealis and aurora australis on the 

 earth. Spots on the sun are produced by the rolling- away 

 from over large surfaces of that luminary of the cloudy en- 

 velope, his photosphere. The effect of such rolling-away is to 

 intensify the action of the sun's gravity upon the earth's 



