[cl ark] 



VISCOSITY OF ETHYL ETHER 



49 



sets of observations taken under the same circumstances. Since the 

 slope is obtained from the slope of the line, it will be seen that the 

 values of the decrement agree very well. For a very large amplitude 

 the motion of the cylinder is not quite isochronous but is accurately 

 so for the amplitudes used. The period does not change materially 

 for a given tube under very different conditions. (See figure 3). 



TUBES AND METHOD OF FILLING. 



The form of the tube used is shown in Figures 1 and 2. This form 

 was adopted in order to study the liquid and vapour regions separately 

 and to retard rather than facilitate the mixture of the materials in the 

 two legs of the tube. Also this form of the tube made it possible to 

 study the viscosity without disturbing the substance in such a way as 

 to mix the horizontal layers. Thus changes with the time can be 

 studied. 



Fig. 2. 



The preparation of the tube is carried outras follows: — The part 

 A is left of full size and straight until after the insertion of the oscil- 

 lating system. After the final washing, the tube is dried with a current 

 of air and when nearly dry is heated very hot inside a coil of wire, the 

 air current still passing. The oscillating system is inserted through 

 A and the tube drawn down to about 1 mm. diameter and bent over. 

 The tube D is sealed on and attached to an aspirator through a cock. 



Sec. Ill, 1915—4 



