IN A CLOSED GALVANIC CIRCUIT. 251 



nesses, which at the same time were perfectly homogeneous, 

 great exactitude in the results could not be calculated upon, and 

 the more so, as it was necessary, in order to obtain plates of the 

 greatest possible homogeneity, to employ none above 6 or 8 mil- 

 lims. thick: in consequence of this the variations in thickness were 

 limited to a few millimetres. The experiments were conducted 

 much as before. After fastening a | — formed tube to the appa- 

 ratus {§ 2) exactly in the manner described in § 5, the tube 

 was provided with a metal cap which could be closed air-tight, 

 and the lateral efflux tube was connected with the manometer 

 (as described in § 7? when using the apparatus before employed 

 in § 3). Afterwards clay partitions of different thicknesses 

 were introduced between the two vessels, the apparatus itself 

 was filled with a solution of sulphate of copper, the brass screw 

 of the metal cap on the | — formed tube was closed, and afler 

 conducting the galvanic current through the apparatus for 

 some time, the height of the mercury in the manometer was 

 read off. 



In one particular case the thickness of the clay plate was d 

 =4-3 milHms., and the mean ratio between the intensity i, of the 

 current and the corresponding height h, attained by the mercury in 



the manometer, was - = 1'73, which made t;i=0'402. When the 



thickness of the plate was decreased to 3*8 millims., we had 



- = 1-60, hence i-,= 0*421. The thickness of the plate was still 



further decreased to 2*8 millims., which made- = 1*21 and 



t 



^-:=: 0*432. Here, therefore, the ratios - decrease in the same 

 id ' ' t 



proportion as d. 



Another plate of the thickness «?=8 millims. gave -=3*30 



and —,=0*41. When the thickness of this plate was diminished 

 id ^ 



to 4 millims,, then - was decreased to 1*62, making t-i=0*40. 



Lastly, the thickness of the plate was still further diminished 

 until it became from 1*7 millim. to 2 millims. thick : we obtained 



T 2 



