Electric Residue in the Ley den Jar 



313 



this case not reduced to the ordinary unit of the instrument ; in 

 the third and fourth columns, stands the observed first elongation 

 E of the galvanometer needle in parts of the scale ; in the fifth 

 the number of parts of the scale calculated from the strong- 

 est charge, as they must have been if the results given by both 

 instruments had completely coincided ; and in the sixth column 

 the difference d, given in parts of the charge. 



These experiments leave no doubt of the fact, that the dispo- 

 sable charge of the battery is tnily given by the sine-electrometer, 

 and hence that the disposable charge of the battery is proportional 

 to the tension of the electricity on the knob of the jar. These 

 experiments were made with Franklin's plate with the same 

 result. 



§4. 



Having thus assured ourselves that the sine-electrometer en- 

 ables us accurately to compare the disposable charges of the same 

 jar with each other, the instrument may be applied to the mea- 

 sui'ement of these discharges if we assume one of them as unit ; 

 the electrometer has its own unit of measure. As stated in 

 Poggendorff's Annalen, vol. Lxxxviii. p. 502, it is the quantity of 

 electricity which, when the repulsion of the magnetic needle by 

 the repelling arm amounts to a certain small angle a, causes the 

 needle to stand at right angles to the magnetic meridian ; and 

 to this unit all results of the instrument, when different needles 

 and different angles of observation are made use of, are reduced. 

 Let us choose, then, as unit, according to which the disposable 

 charge of any jar is to be measured, the quantity of electricity 

 which must be present in order to cause the electrometer to 

 exhibit its own unit ; then the numerical results of the latter 

 sene immediately as the measure of the disposable charges for 

 this particular jarf. 



* This charge consisted of a residue which had again made its appear- 

 ance. 



t It is here manifest that an absohite measure is not attained; for. 



