Experiments with Rotating Viscous Liquids. 255 



very close consistency between series of observations taken 

 on different days. In our experiments, as a matter of fact, 

 the temperature did not vary more than 1° C. during a 

 >erie< of observations made on any particular day. As tar 

 as possible, each series was completed on the same day as 

 it was begun. It' this was not possible, the last reading 

 was repeated. This accounts for one or two small discre- 

 pancies between two determinations of the same point on 

 some of the graphs given below. 



Here is a sample of observations taken quite at random 

 from a laboratorv notebook, in order to show the decree 

 of consistency between consecutive readings. 



Small druin with cycle-lamp oil ; temp. 15°-4 C. 



Volume of oil in drum= 120 c. c. 



Load hung on cord = 100 grms. 



Load at top : scale-reading of iudex-pin = 218*8 cms. 



Load at bottom: „ „ =38*4 cms. 



.-. H = 218-S-38-4 

 = 180-4 cms. 



Consecutive scale-readings of height of rise of load : — 

 101-2 cms. 

 101-1 „ 

 101-1 „ 

 Mean = 101-1 cm. 

 .-. h = 101-1-38-4 

 = 62-7 cms. 



For the times of fall were found : — 



5*30 (metronome) sees. 

 5-36 „ „ 



Mean = 5-33 „ „ 



The factor of reduction to mean solar seconds is 1-058. 

 From the above data we get 



f=47*6 grms.-weight. 

 The value of /' for the empty drum was previously found to be 



= 10*6 grms.-weight. 



.-. friction due to presence of liquid in the drum 

 = 37'0 grms.-weight, approximately. 



Experimental Results. 



So far as concerns the general form, the results exhibited 

 in the graph- may be taken as correctly representing the 

 behaviour of the viscous liquids used in these experiments. 



