572 
MR. W. C. D. WHETHAM ON THE ALLEGED SLIPPING 
Pi 'essure varying. 
Levels I 26-57 . 7-37 cms. 
L 20 - 06 J 
Temperature, 16°-4 ; 16°-6.. 16°-5 
Time, 6' 0"; 10' 37".4' 37" 
Value of p..-01241 
Levels {"^’^^’126-56 . . 
121-781 
Temperature, 16°-5 ; IG^'-o 
Time, 1' 0" ; 7' 7" . . . 
Value of p. . 
5-64 cms. 
16°-5 
6' 7" 
•01258 
Pressure constant. 
Levels, 23-42 ; 26-56 . 3-07 cms. 
Temperature, 16°-5 ; 16°-6.16°-6 
Time, 7' 0"; 18' 33".11' 33" 
Value of p.-01293 
Levels, 21-56 ; 26-56 ... 5-00 cms. 
Temperature, 16°-6 ; 16°-6.16°-6 
Time, 0'0"; 6' 54" ..6' 54" 
Value of p .-01258 
Pressure varying. 
Levels 26-56 . . 
123-48 J 
Temperature, 16°’6; 1 6°-6 
Time, 7' 0" ; 15' 59" . 
Value of p 
3-93 cms. 
16°-6 
8' 59"rf 
•01288 
Thus the experiments, both with the glass and with the copper tube, show that 
the time of flow is the same if the pressure be allowed to fall, as it is if the pressure 
he kept constant at the mean value of the falling pressure. 
The results also show that the copper tube gives a value for p practically identical 
with that given by the glass tube, and a little greater than that given by Poiseuille’s 
experiments, instead of about five times less. 
The effect of modifying the interior surface was then investigated. Tubes were 
cleaned with acids and alkalies, poli.shed with emery powder, coated with a film of oil, 
and amalgamated with mercmy. 
