THE SMITHSONIAN INSTITUTION. 



183 



height, namely, 2.75 centimetres) was increased by the values in the 

 first column : 



Distance of plates, 

 centimetres. 



2.5 



5.0 



7.5 



12.5 



25.0 



Coils removed. 



2.11 

 4. 25 



6.98 

 10. 75 

 20. 67 



Since the corresponding numbers of the two columns here liave 

 nearly the same ratio throughout, the resistance of the fluid column 

 is thus actually proportional to its length. In the mean we get from 

 this experiment, for the resistance of a stratum of li(|uid of five cen- 

 timetres, the value 4.3 rheostat coils. 



When the trough was filled to a height of 4.8 centimetres, the value 

 2.5G rheostat coils was obtained from a similar experimental series for 

 the resistance of a liquid column five centimetres long of the same 

 dilute acid. 



Now, since the heights of the liquid in the trough, 2.75 and 4.8, 

 are nearly in inverse proportion to the corresponding resistance 4.8 

 and 2. 50, (namely, 2.75 : 4.8= 2.56 : 4.4(i,) the resistance of the 

 liquid column is in inverse ratio of its section. 



The following table contains the values determined by Horsford, for 

 the specific resistance of difierent liquids : 



Name of licmid. 



Sulphuric acid 



Do 



Do 



Do. 



Do.... 



Do 



Solution of chloride of sodium 



Do.. 



Do 



Do. 



Solution of cliloride of potassium. 

 Solution of sulphate of copper 



Do 



Solution of sulphate of zinc. 



Condition. 



Specific gravity 1. 10. 



do.. 1. 15. 



do 1.20. 



do 1.21 



do 1.30.. 



do 1.40 



27. {> grains in 500 cc. water . . 



21.3 do do. 



10. C5 do do 



5. 325. ..do do 



27.7 do do 



Of which 100 cc. contains 



15.01)3 grains 



With douhle volume water . . 



Of whicli 100 cc. contains 



7. 2587 grains 



Specific resistance, 

 that of silver :rr 1 . 



938,500 



840. 500 



69 (i. 700 



696. 700 



696. 700 



1.02;j,400 



7, 157.000 



9,542.000 



18,460.00(1 



34, 110,000 



7, 168,000 



12,058.00(1 

 17,490,000 



23,515,000 



These liquids were chemically pure. 



