[Thompson] 



ADVANCE OF THE RIPPLE 



131 



the advance of the ripple varied to a great extent. This was found to 

 be due partly to shaking, or slightly jarring the tube T, and was 

 eliminated to a large extent by connecting the opening through a tap 

 F by rubber tubing to a tap G fastened to a clamp separate from those 

 holding tube T. The velocity was now varied and the advances of 

 the ripple measured. The diameter and length of the tube used were 

 2-95 and 90 cms. respectively. The selected point was 17 cm. above 

 the level of the water in the dish. The results are tabulated below 

 and a graph is plotted as shown in Fig. 4. The advances used arethé 

 averages of five readings with deviations of 1 millimetre, approximately. 



Advance of Ripple in cms. 

 I8r 



.8 10 m 1^ W 



Velocity of moving surface cms. per sec. 

 Figure 4 — Relation between the advance of ripple and the velocity of moving surface . 



Table I — Relation between the Advance of Ripple and the 

 Velocity of Moving Surface 



For greater velocities than those used, it was impossible to make 

 measurements, and for lesser, the ripple disappeared due to the water 

 draining from the sides of the tube. Tap water was used. 



