AT THE BOUNDARY OF A LIQUID IN MOTION. 
571 
experiments, during which the level was kept constant by allowing water to flow into 
A at the same rate as it flowed out. 
A glass tube was first used (r = '0568 cm., I = 22'53 cms.). 
Pressure constant. 
Level of reservoir, 19‘30l 
y.10'93 cms. 
,, orifice, 30'23 j 
Temperature, 18°T ; 18°'l.18°'l 
Time: start, 6' 0"; finish, 17' 28".11' 28" 
Value of the coefficient of viscosity /x, deduced from 
this by Poiseuille’s formula.'01339 
Pi 'essure varying. 
T 1 r • [Start, 18'47K.oJ 
Level ot reservoir f f 19'35 I 
iFinish, 20'22J f.10'59 cms. 
,, orifice.30'24 J 
Temperature, 18°'l ; 17°'9.18°'0 
Time: start, 8' 0"; finish, 19' 32".11' 32" 
Value of /X.'01341 
A copper tube was then substituted. 
Tube No. 5. — (r = *0836 cm., I — 30'86 cms.) 
Pi 'essure constant. 
Levels, 20'05 ; 26'57. 6'52 cms. 
Temperature, 16°'4 ; 16°'4.16°'4 
Time: start, 0' 0"; finish, 5' 51". 5' 51" 
Value of/X.'01391 
4 D 2 
