380 



MESSRS. V. H. VBLEY AND J. J. MANLEY ON 

 Diagram I. 



Showing general aiTangement of the apparatus. 



No. 18 copper wire soldered on to massive copper tags ; their resistances were deter- 

 mined in position and found to be as nearly as possible equal ; L 3 the leads (of 

 similar construction) to the standard coils were of resistance '005 ohm., a constant 

 factor added to all values of II. 



THE ELECTROLYTIC CELLS. 

 (i.) Standard Cell. 



Several forms of cell were adopted in the earlier ex-periments, but as all those of 

 the U or bottle pattern, as described by KOHLRATJSCH, involve their calibration by a 

 solution of an electrolyte of known conductivity, it was resolved to use a cell of a 

 straight burette form, with one electrode fixed, and the other movable, so as to 

 throw different lengths of the acid into circuit, and thus obtain independent 

 measurements. For this purpose the movable electrode was welded on to a 

 platinum wire passing through a glass tube to the binding-screw, S (fig. 4) ; 

 above this a similar tube was fastened, upon which was etched a centimetre scale 

 copied directly from the standard. In order to ensure that the whole arrangement 

 should slide parallel to its axis, the graduated tube was allowed to run in V grooves 



