# Who discovered fluid visocity?

Who discovered fluid viscosity and what is the history behind the concept of fluid viscosity? Further, who first defined or parametrized viscosity as shown in Equation 1.1-2 below?

Equation 1.1-2 (below) of the textbook Transport Phenomena by Bird, Stewart, and Lightfoot is given with the following footnote:

$$\tag{1.1-2} \tau_{yx}=-\mu \frac{dv_x}{dy}$$

Actually Eq. 1.1-2 does not appear in Sir Isaac Newton's Philosophiae Naturalis Principia Mathematica, but the germ of the idea is there. For illuminating comments, see D.J. Acheson, Elementary Fluid Dynamics, Oxford University Press, 1990., Sec. 6.1

I do not have Acheson's book.

• I'd probably say who "defined, or parametrized" viscosity. People knew a zillion [arbitrary time unit] ago that tree sap flowed slower than water. :-) – Carl Witthoft Jan 28 at 13:33