138 



Dr. A. Oberbeck on the Friction 



only about relative measurements, I have not thought it neces- 

 sary to take account of it separately. 



5. I communicate first those experiments which concern the 

 testing of the method employed. As was remarked above, it 

 was requisite to determine how far the oscillation-period and 

 the logarithmic decrement are dependent on the quantity of 

 the amplitude. The following table (Table I.) contains the 

 results of three series of experiments. The above-described 

 appai'atus having been set oscillating, and having already 

 executed a series of oscillations, the turnings towards both 

 sides were noted, and therefrom the initial amplitudes deter- 

 mined ; at the end of four oscillations the final amplitude was 

 obtained in the same manner : both numbers are given in the 

 first column. From them the decrement \ was calculated. 

 At the same time the periods of the four oscillations were 

 ascertained and the mean taken, which is returned under T. 

 Here the above-described rectangular vessel was employed, in 

 which the movable plates faced each other at a distance of 15 

 millims. The vessel was filled with distilled water, into which 

 dipped a rectangular brass plate 100 millims. long, 5 millims. 

 high, and 0'5 millim. thick. During series A the plate was 

 entirely in the interior of the liquid ; during B the upper edge 

 exactly intersected the free surface, while during C it projected 

 0*5 millim. above. The oscillation-period T is given in seconds. 

 The quantity \ is the difference of the ordinary logarithms. 



Table I. 



A. 



B. 



Amplitudes. 



T. 



X. 



Amplitudes. 



T. 



X. 



424 378 

 337 303 

 280 252 

 227 205 

 185 167 



11-50 

 11-65 

 11-45 

 11-50 

 11-50 



001247 

 001155 

 001144 

 001132 

 0-01086 



420 321 

 353 271 

 244 190 



11-85 

 11-50 

 11-80 



002919 

 002870 

 002716 



Mean . 



.. 11-72 



Mean ... 1152 



C. 



Amplitudes. 



T. 



X. 



502 390 

 324 256 

 216 172 

 146 117 



12-5 

 123 

 12-7 

 12-3 





 

 







02741 

 02558 

 0-02475 

 002379 





12-4 



5 









