450 OHM ON THE GALVANIC CIRCUIT. 



the word conductibility occurs without any closer definition, the 

 absolute conductibility is always to be understood. 



Hitherto we have left out of consideration the change which 

 the disk suffers from the adjacent atmosphere. This influence 

 may easily be determined. If, for instance, we designate by c 

 the circumference of the disk belonging to the abscissa w, then 

 c d X is the portion of its surface which is exposed to the air ; 

 consequently, according to the experiments of Coulomb, men- 

 tioned in § 9, 



b c u dxf d t 



is the change of the quantity of electricity which is occasioned 

 in the disk M by the passing off of the electricity into the at- 

 mosphere during the moment of time d t, where b represents a 

 coefficient dependent on the cotemporaneous nature of the 

 atmosphere, but constant for the same atmosphere. It expresses 

 a decrease when ti is positive, and an increase when u is nega- 

 tive. But in accordance with our original supposition, this 

 action cannot occasion an inequality of the electroscopic force 

 in the same section of the body ; or at least, this inequality must 

 be so slight that no perceptible alteration is produced in the 

 other quantities ; a circumstance which may nearly always be 

 supposed in the galvanic circuit. 



Accordingly, the entire change wliich the quantity of elec- 

 tricity in the disk M undergoes in the moment of time d t is 



X w dx . dt — b c u dx dt, 



dx- 



in which the portion is comprised which arises from the motion 



of the electricity in the interior of the body as well as that 



which is caused by the circumambient atmosphere. 



But the entire change of the electroscopic force u in the disk 



M effected in the moment of time dt is 



du ,, 



dt 



consequently the total change in the quantity of electricity in 



the disk M during the time dt is 



du J J. 



CO — -— ax at, 



dt ' 



where, however, it is supposed that under all circumstances 



similar changes in the electroscopic force correspond to similar , 



changes in the quantity of electricity. If observation showed 



that different bodies of the same surface imderwent a different 



