8 UNIVERSITY OF MISSOURI STUDIES 



The question is this : What will happen to the particles of fluid 

 in the tube when the stirrup moves slightly inwards or out- 

 wards? This is a problem' which can be answered either 

 on the basis of our general knowledge of similar processes 

 or by means of a special experiment. Let us first try the 

 former way. When the stirrup is pushed inwards and the 

 round window outwards, the liquid near the windows must 

 certainly move in the direction indicated by the arrows in the 

 figure. Of course, the direction of the movement would be 

 the opposite if the movement of the stirrup changes its sign 

 and pulls instead of pushes. But what would happen in the 

 fluid at the other end of the tube? At x or even at y? The 

 answer to the question is simple : Nothing would happen. 

 No movement of any kind could possibly occur there, since 

 there is no sufficient cause why any movement should occur. 

 The friction of the fluid against the walls of the tube, which is 

 quite considerable in a narrow tube, must prevent any spread- 

 ing of the disturbance beyond a very near limit. That is, when- 

 ever the stirrup moves back and forth, those particles of the 

 fluid which are in the nearest path leading from the oval 

 to the round window must move accordingly. All the rest 

 of the fluid remains motionless. 



In order to demonstrate the facts just mentioned to those 

 finding difficulty in understanding that from the general laws 



of hydromechanics nothing else could re- 

 A simple suit in the case in question but what we 



experiment have just described, we may perform the 



following experiment. A box containing 

 white clay in a plastic condition has two circular openings 

 on one side, not far from each other, as shown by figure 4 

 in cross-section. We now press, by means of a piston, 

 into one of the openings, A, a small quantity of colored clay, 

 then a small quantity of white clay, and again colored clay 

 until the latter becomes visible on the outside of the box 



