oOO WRITINGS OF JOSEPH HENRY. [1855- 



in which, while the air was highly positive, the earth was 

 negative, and the bodies carried up were repelled from the 

 earth and attracted by the cloud, as in the case of the dan- 

 cing figures between the two plates, one of which is connected 

 with the prime conductor of an electrical machine and the 

 other with the earth. We think however with Mr. Espy 

 that electricity is altogether a collateral result, — an efifect of 

 the storm and not its cause; it is probable however that its 

 presence tends to modify the appearance and produce phe- 

 nomena of a subordinate character. It is well known that 

 when a kite to which is attached a metallic string is sent 

 up to a considerable height above the earth, the wire be- 

 comes highly charged with electricity, even in a clear day 

 when not a cloud is visible; this effect is due to what is called 

 induction. The positive electricity of the upper atmosphere 

 drives the natural electricity of the wire from its top to its 

 bottom, hence the upper end of the wire will be negative 

 and the lower end positive; a similar effect must be pro- 

 duced on the cloud formed by the uprising column and on 

 the column itself, the two form a continuous conductor of 

 immense height, and hence like the wire must become 

 charged at the lower end with positive electricity of great 

 intensity, which will tend to elongate the trunk downwards 

 by repulsion, and which will give occasional discharges to 

 the earth as the tornado passes over good conducting sub- 

 stances. 



The terrific and appalling grandeur of the tornado strikes 

 the beholder with astonishment and awe, now pausing fit- 

 fully as if to select with malignant caprice the objects of its 

 unsparing fury, now descending to the earth, and again 

 drawing itself up, with its deep, loud, and sullen roar; its 

 mysterious darkness; its apparent self-moving, resistless rev- 

 olutions ; carrying upwards branches of trees, beams of 

 houses, and large objects of every description ; its impetuous 

 downward rush to the earth, and then again up to the sky, 

 its sublime altitude, sometimes erect and at other times in- 

 clined; its reeling and sweeping movements; all these and 

 more to be adequately conceived must be actually witnessed. 



