316 WRITINGS OF JOSEPH HENRY. [1855- 



a portion of the natural electricity of the cloth is transferred 

 to the glass ; the latter receives a positive charge of elec- 

 tricity, while the woollen cloth loses a portion of its natural 

 share of the fluid, and assumes the negative state; and since 

 the slips of glass, as well as the surrounding air, are non- 

 conductors, the redundancy of the one cannot escape, nor 

 the deficiency of the other he supplied, and therefore the 

 charged condition of each will continue for a considerable 

 time, particularly if the air be perfectly dry. 



When the glass plate is made to touch the ball a portion 

 of electricity accumulated on the surface of the former is 

 transferred to the latter, which has then more than its natu- 

 ral share ; and since atoms of free electricity repel each 

 other, the ball will apparently be repelled from the glass ; 

 and also because there is an attraction between free elec- 

 tricity and un-saturated matter, the cloth which is in this 

 condition will attract the same ball. When the two slips 

 of glass are brought together and presented as a whole the 

 attractions and repulsions may still be considered as exist- 

 ing, but since they are equal and opposed they entirely 

 neutralize each other, and no external effect is perceptible. 



The neutralization of the two opposite forces in this ex- 

 periment affords an illustration of the condition of a body 

 in its natural state. Although it contains a large amount 

 of the fluid no action is produced on other bodies in their 

 natural condition because the attractions and repulsions just 

 balance each other. 



For exhibiting the most important statical phenomena of 

 electricity, and for verifying the deductions from the theory, 

 we may employ a solid glass rod of about fifteen inches in 

 length, and a rod of sealing-wax or of gum shellac of the 

 same length. If these be well dried, held by one end and 

 rubbed with a piece of woollen cloth at the other, electrical 

 excitement will be produced. Instead of a solid glass rod 

 a tube may be employed, provided the interior be perfectly 

 dry, and well corked to prevent the access of moisture. If 

 the end of the tube or rod be rubbed, and afterwards brought 

 into contact with a small ball of pith, or of any light con- 



