New Oiitrine'i of Chemical Philosophy. 431 



The ball, in its natural state, contains the two elements of 

 electricity, thermogen and photogen, diffused over its surface : 

 consequently, if the tube be charged with thermogen (positive 

 electricity) it will repel that element from the surface of the ball, 

 because elements of the same kind repel each other ; but the 

 other element, photogen, will remain upon the surface of the 

 ball undisturbed. 



To prove the truth of this theory by experiment, I placed an 

 electrometer with the top of its wire in contact with the under- 

 side of the ball ; and a barometer-tube, rubbed with silk, being 

 brought so near the ball as to electrify it by induction, the leaves 

 of the electrometer diverged, containing thermogen. 



This electrometer and the excited tube were taken away from 

 the ball, and another electrometer being applied to it became 

 electrified, but in a state contrary to the former. 



Thus, the two electrometers became permanently electrified, 

 by the two elements which the ball possessed in its natural state. 

 The first electrometer received a portion of thermogen which was 

 repelled from the ball by the excited tube, but the other was 

 electiified by the photogen which remained upon the ball after 

 the tube had been removed. 



Exp. 7. Two Dutch-leaf electrometers, being placed upon a 

 table at the distance of about an inch asunder, and an excited 

 barometer-tube held over them at the distance of about two 

 indies from each, became permanently electrified. One of them 

 received the same element as the excited surface, but the other 

 received the contrary element. 



Explanation. 



All the metal contained in one of these electrometers, No. 1, 

 weiglis only three grains, and consequently the quantity of elec- 

 tricity which it contains in its natural state may be deemed 

 almost nothing ; wherefore electrometers of this construction 

 always receive that element to which they are exposed, whether 

 they receive it by induction or direct communication*. 



But the other electrometer, No. 2, had a brass ball of an inch 

 in diameter fixed upon the top of it ; and as soon as the excited 

 tube was brought near it, the two elements which were diffused 

 over its surface, in its natural state, began to be separated. The 



* If this cicctioiiictcr be brous^ht into a room coiitnining an atmosphere 

 of tlierinoi^en f positive electricity), its leaves will diverge witli that element 

 to an aiij^lc contaiiiiiig between 90 and 180 degrees. Then, if it be carried 

 into another room, sonic time will elapse before any diminution in the ao- 

 j:lc contained by the leaver can be perceived; but thii time will depend 

 ujion the perletlion of the initruuitni. 



element 



