132 THE ROYAL SOCIETY OF CANADA 



As the water ascends the tube the advance of the ripple increases, 

 and as it nears the top it lengthens out very rapidly and finally dis- 

 appears. This seems to be due to the draining away of the water 

 from the walls of the tube and thus changing the thickness of the 

 layer of liquid on the wetted wall. To study this, the water was 

 allowed to ascend the tube at a definite velocity of 20 cm. in 25 seconds. 

 This time varied somewhat but never more than -4 seconds. The 

 tube was 90 cm. long and had a diameter of 2 • 5 cm. The water was 

 allowed to rise 80 cm. in the tube and measurements were taken at a 

 point 17 cm. from the starting point or lower surface. The tube was 

 allowed to drain for a definite length of time before commencing each 

 operation. The results of readings taken on three different occasions 

 are tabulated below and graphs (1, 2 and 3) are plotted as shown in 

 Fig. 5. The advances used are the averages of five readings with 

 deviations of 1 millimetre, approximately. Fresh tap water was used 

 on each occasion. 



