in Free Surfaces of Liquids. 



141 



similar manner. The following slightly differing values were 

 obtained: — 



Pure water surface .... 1248 

 The same with oil . . . .1301 

 The same with turpentine . . 1119 

 while on using the narrowly separated plates (e= 15) a scarcely 

 visible layer of oil sufficed to make the resistance to the motion 

 so great that the movable system returned, without oscillations, 

 to its position of equilibrium. According to this, the use of a 

 laterally narrowly limited vessel is found to be absolutely 

 necessary with the oscillation-method employed. 



6. This previous question being settled, I proceed to the 

 comparison of the resistance of the interior and of the surface 

 with different liquids. Most of the experiments were exe- 

 cuted with the most favourable distance of 15 millims. between 

 the plates, by means of the repeatedly mentioned brass plate 

 of 100 millims. length; but I have not omitted to make some 

 experiments also with the greater distance of 20 millims., as 

 well as to use instead of the brass plate a brass cylinder of the 

 same length and about 5 millims. in diameter. 



The following Tables III., IV., V. (which are quite intelli- 

 gible after the previous explanations) give only the values of 



7^ as measuring the resistance. For the last table I may fur- 

 ther remark that / signifies a previous filtration, and that the 

 numbers standing with the names of the liquids represent 

 their specific gravities. 



Table III. Rectangular brass plate. 



Distance between the glass sides 20 millims 





Liquid. 



A = 10 mm. 



h = b mm. 



^ = 0'5 mm. 



^=0 mm. 



^=— 0*5 mm 



Distilled water ... 



Distilled water "1 



filtered J 



1081 

 1021 



1106 

 1143 



1310 

 1277 

 1155 



2045 

 2355 

 1024 



2026 

 2451 

 1016 





Table IV. Brass cylinder. 

 Distance between the side plates 15 millims. 



Liquid. 



h = 5 mm. 



^=0"5 mm. 



h — mm. 



h = — 0'5 mm. 



Distilled water 1 



Distilled water 2 



Alcohol 



1131 



1331 



1875 



1614 

 1574 

 1512 

 2327 



3388 

 3301 

 1396 

 2107 



4074 

 3613 

 1293 

 1899 



Oil of turpentine 



