On the Resistance to the Uniform Motion of a Solid Through a Viscous Liquid. II.

Abstract

This paper constitutes the author's answer to some adverse criticisms by John T. Burwell, Jr., of an earlier paper having the same title and reporting evidence for the assumption of liquid slip at the surface of a solid in motion through a viscous liquid. The importance of the results contained in the earlier paper to viscosimetry by the rolling‐ball method is emphasized. This relation exists because the author's apparatus was essentially a rolling‐ball viscosimeter. References are given to independent studies by other investigators which also support the hypothesis of liquid slip. The possibility of the phenomenon's being apparent, only, is brought out by presenting two other interpretations of the author's observations. A new and more accurate method for converting time of roll into viscosity of the liquid than the current graphical one is presented for the rolling‐ball viscosimeter, together with an apparent reason for believing that the calibration curve of this viscosimeter may not always be independent of pressure. The author's reasons for considering this new source of error in the use of the rolling‐ball apparatus for high pressure viscosimetry to be actually non‐existent are given. And finally the author describes an original method for checking the validity of the hypothesis of liquid slip in the case of the rolling‐ball viscosimeter that is entirely different from the method he used in his earlier paper.