-1859] WRITINGS OF JOSEPH HENRY. 359 



a portion of the natural electricity of the air, and thus pro- 

 duce at the lower end of the wire a series of sparks following 

 each other, after the lapse of a certain time, at regular 

 intervals. 



From the foregoing it will be evident that in interpreting 

 the indications of the two classes of instruments we have 

 described, (which may be denominated those of induction 

 and those of absorption,) we must keep constantly in view 

 the principles that have been explained; and it is for want 

 of a clear appreciation of these principles that so much com- 

 plexity has been introduced in describing the otherwise 

 comparatively simple effects of induction. 



Electricity of the clouds. — The explanation of the thunder- 

 storm and the tornado given by Peltier does not appear to 

 us as satisfactory as could be desired. In common with 

 most of the meteorologists of Europe, he fails to take into 

 consideration the real character of the storm, which as 

 "we think has been fully established by theor}'' and observa- 

 tion in this country, as consisting in the rushing up of the 

 lighter air to restore the normal equilibrium of the atmos- 

 phere, disturbed or rendered unstable by the gradual intro- 

 duction next to the ground of a stratum of warm and moist 

 air. As an illustration of this disturbance, we may mention 

 the fact pointed out to Arago, by Captain Hessard, as ob- 

 served by him in the Alps, namely that during great heats 

 there take place suddenly at the lowest stratum of clouds, 

 upward rushings, extending vertically like rockets. 



We shall endeavor to supply the deficiency we have men- 

 tioned in the exposition of Peltier, and to present on the 

 principles of the induction of the earth in connection with 

 the upward motion of the air, a logical explanation of the 

 origin and continued supply of the great quantity of elec- 

 tricity developed in the meteors under consideration. 



It follows from the principles of induction, that the upper 

 end of all perpendicular insulated conductors must be electri- 

 fied negatively, and the lower end positively, since the attrac- 

 tion of the un-saturated matter of the earth below will draw 

 down the natural electricity of the conductor into its lower ex- 



