Discussion L. J. BRADFORD. 6 Advances in science are made in three stages; (a) New phenomena are observed, (6) these phenomena are studied to discover and interpret their meaning, and (c) the phenomena are usefully applied. The late Prof. Norton and his associates have, in the work described in this paper, accomplished the first of these. The interpretation and application of these data will follow. In the development of these phases, all those interested in the work should participate.

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... ion of Figs. 16 to 19, inclusive, indicates that in all cases the curve of rate of shear plotted against shearing stress is substantially a straight line passing through the origin for a pressure of 10,000 psi. It may be concluded that this is also true for all lower pressures. At 14,000 psi this condition ceases. The rate of shear rises more rapidly than does the shearing stress, and the curve is concave. Extrapolation of the curves for this and greater pressures yields an intercept on the shear-stress axis. They are clearly the curves of plastic substances. Curves for 18,000 psi in Fig. 16 , and for 18,000, 23,000, and 27,000 psi in Fig. 17 , show another peculiarity. It will be seen that each is composed of two substantially straight lines joined by a curve. It is quite possible that the other curves would show the same characteristic had they covered wider ranges of shear stress. This suggests that the oils investigated pass from New-