AMPLIFICATION OF THE LAW OF POI&EUILLE 45

that the formula P. = KIn may be used in the critical regime.

Reynolds has compared the data of Darcy for large tubes,

that of Poiseuille for small tubes, with his own, plotting the

logarithmic homologues as in Fig, 13. The result is shown in

_____L.

FIG. 16.—Detail of coaxial viscorneter.
Mg. 14. Each line represents the logarithmic homologue for
some particular tube, described in the figure. It is at once
apparent that, for the most part, experiments have "been made
well below or else well aboTe the critical values. In the small
tubes of Poiseaille the velocities were below the critical values.