ATMOSPHERIC ELECTRICITY. 



149 



ATMOSPHERIC ELECTRICITY. 



Among the innumerable relations of the electric fluid with the phenomena 

 of nature, there are none which present so many circumstances of general in- 

 terest as its connexion with the various states and appearances of the atmo- 

 sphere. Indeed, it were difficult to name any atmospheric change which is 

 not directly or indirectly connected with electric agency. It is true that these 

 phenomena, fugitive and transitory as most of them are, have not been, in every 

 case, traced to their causes ; that the relation of many of them to the agency 

 of electricity is rendered probable from general appearances, rather than dis- 

 tinctly and satisfactorily demonstrated ; that some of them, which are evidently 

 of electric origin, nevertheless have not been explained by or reduced to any 

 of the known laws which govern that physical agent ; still, there is much that 

 falls under the general principles of electrical science ; and those phenomena 

 which remain without any, or without satisfactory explanation, require to be 

 stated, that those who pursue this part of physical science, with the view to 

 extend its limits, may be guided to the proper subjects of observation and in- 

 vestigation. 



We shall first, then, state generally the apparatus used for observing tie 

 electric state of the air, and shall next proceed to explain the results at which 

 those philosophers have arrived whose attention has been directed to atmo- 

 spheric electricity. 



APPARATUS FOR OBSERVING THE ELECTRICITY OF THE ATMOSPHERE. 



To construct a stationary apparatus for observing the electric state of the 

 air, let a rod of iron, from twenty to twenty-five feet in length, be erected at the 

 top of the building in which the observatory is placed, and let it be carefully 

 insulated at the points where it meets the roof and other parts of the build- 

 ing. The lower parts of this rod should be in metallic communication with an 

 electroscope placed in the observatory, by means of a chain or bar capable of 



