140 



Dr. A. Oberbeck on the Friction 



Table II. 



h. 



e = cc . 



e = 30 millims. 



T. 



\ 

 T* 



T. 



\ 

 T' 



millim. 

 + 5 

 + 0-5 





 -05 



11-28 

 11-28 

 11-31 



11-22 



1172 

 1245 

 1248 

 1222 



11-22 

 11-58 

 11-56 

 11-36 



1085 

 1119 

 1632 

 1754 



h. 



millim. 

 + 5 

 +0-5 





 -0-5 



e = 20 millim s. 



e=15 millims. 



T. 



\ 



T. 



X 

 T 



11-00 

 1100 

 11-24 

 11-84 



1143 



1277 

 2355 

 2451 



11-42 

 11-44 



11-82 

 12-68 



1188 

 1567 

 2649 



2784 



The different series of experiments were made at different 

 times; and hence, in the first place, only the numerical values 

 of each series are comparable among themselves. Neverthe- 

 less the frictional resistances show for the motion at the 

 greater depth (h = 5 millims.) a sufficiently good accordance; 

 they are at all events not considerably influenced by the shape 

 of the vessel. This influence, however, becomes already pro- 

 minent as soon as the plate approaches near to the free sur- 

 face (A = 0*5 millim.), and becomes very considerable when 

 the upper edge cuts the free surface. While in the first 

 series the resistances remain the same, in the rest a sudden 

 increase takes place when the plate is raised to the small 

 extent of 0*5 millim.; and is the greater the nearer the bound- 

 ing plates are. Of this great influence of the limitation of 

 the vessel upon the resistance, the causes of which I have pre- 

 viously explained, I sought to convince myself in still another 

 way. 



After the resistance of a surface of pure water in the 

 vessel in which there is no perceptible influence of the sides 

 had been once more determined (A = 0), the surface was 

 covered with a thin layer of oil spread as uniformly as possible 

 by stirring, and the resistance again investigated. Finally, 

 the same experiment was repeated; but onto the pure water 

 surface a thin layer of oil of turpentine was brought in a 



