:;92 



Mr. 0. Reynolds. 



[Mar. 15, 



(2.) If the water in the tank had not quite settled to rest, at suffi- 

 ciently low velocities the streak would shift about the tube, but there 

 was no appearance of sinuosity. 



(3.) As the velocity was increased by small stages at some point in 



the tube always at a considerable distance from the trumpet or intake, 



the colour band would all at once mix up with the surrounding water, 



and fill the rest of the tube with a mass of coloured water, as in no-. 4 



7 o 



Fig. 4. 



Any increase in the velocity caused the point of breakdown to 

 approach the trumpet, but with no velocities that were tried did it 

 reach this. 



On viewing the tube by the light of an electric spark, the mass of 

 colours resolved itself into a mass of more or less distinct curls 

 showing eddies, as in fig. 5. 



Fig. 5. 



The experiments thus seemed to settle questions 3 and 4 in the 

 affirmative — the existence of eddies and a critical velocity. 



They also settled in the negative, question 6 as to the eddies 

 coming in gradually after the critical velocity was reached. 



In order to obtain an answer to question 5 as to the law of the 

 critical velocity, the diameters of the tubes were carefully measured, 

 also the temperature of the water and the rate of discharge. 



(4.) It was then found that with water at a constant temperature 

 ,and the tank as still as could by any means be brought about, the 

 critical velocities at which the eddies showed themselves were exactly 

 in the inverse ratios of the diameters of the tubes. 



(5.) That in all the tubes the critical velocity diminished as the 

 temperature increased, the range being from 5° C. to 22° C. and the 

 law of this diminution, so far as could be determined, was in accor- 

 dance with Poiseuille's experiment. 



Taking T to express degrees Centigrade, then by Poiseuille's 

 •experiments — 



^oc P=l + 0'0336T + 0-00221 T*, 

 P 



