44 
MR. A. MALLOCK ON EXPERIMENTS ON FLUID VISCOSITY. 
The Table II. (pp. 48-52) contains the results of all the experiments (except a few 
made with the medium cylinder E') as obtained directly from the analysis of the 
diagrams taken with the camera-lucida. 
These results were afterwards corrected for the variation of the depth of the fluid 
in contact with the suspended cylinder, due to the curvature of the free surface, and 
further corrected for the difference, if any, of this depth from 8’5 inches (a value 
which the dimensions of the cylinder rendered convenient). Most of the quantitative 
results are summarized in diagrams 5, 6. and 10. 
In Diagrams 5 and 6, and also in Diagrams 4, 8, and 9, the abscissa is the number of 
revolutions per minute of the revolving cylinder and the ordinates are the readings of 
the divided circle on A. 
In Diagrams 5 and G, in addition to the number of revolutions per minute, the 
velocity (in feet per second) is given, which two parallel planes must have with 
reference to one another, if their distance apart is equal to the width of the annulus, 
and the fluid between them is distorted at the same rate as the fluid at the surface of 
the cylinder A. 
In Diagrams 4, 5, and 6, it will be seen that up to a certain velocity of the 
cylinders E and E', the ordinates increase almost exactly as the velocity. Above 
this velocity, and until a considerably higher velocity is reached, it appears that the 
ordinates may have any value between certain limits. 
At the higher velocities the readings obtained for the ordinates again become very 
precise and constant, but lie on a curve instead of a straight line. This curve, if 
continued in the direction of decreasing velocities, will be found to form the upper 
limit of the value for the ordinates in that part of the diagram where the readings 
are fluctuating, the lower limit being the continuation of the straight line which 
precedes it. 
The curves of Diagram 7 record the motion of the cylinder A, from the moment of 
the starting of E until the fluid in the annulus has assumed the steady motion 
appropriate to the velocity at which E is being driven ; and they show that, whether 
the velocity of E is large or small, provided it does not exceed 150 feet per minute 
about, the steady motion state is reached in approximately the same time. 
The curves of Diagram 7, as immediately obtained from the camera-lucida tracings, 
are partly obscured by the natural oscillation of the cylinder on its torsion wire, but 
these oscillations have been eliminated, and the curves show the zero about which the 
oscillations are taking place, at each instant. 
The curves on Diagram 8 are given to show that both the mercury and the short 
cylinder K have a great effect in increasing the range through which the transmitted 
moment varies as the first power of the velocity. 
Diagram 9 contains the results of the experiments of series (2), in which the outer 
cylinder (E') was suspended by the torsion wire while the inner cylinder (A) revolved. 
