## Abstract

The integration of the equation of the boundary layer $\frac{\partial ^{3}f}{\partial \sigma ^{3}}$+f$\frac{\partial ^{2}f}{\partial \sigma ^{2}}$=$\lambda \left[1-\left(\frac{\partial f}{\partial \sigma}\right)^{2}\right]$ + 2$\gamma \left[\frac{\partial f}{\partial \sigma}\frac{\partial ^{2}f}{\partial \sigma \partial \gamma}-\frac{\partial f}{\partial \gamma}\frac{\partial ^{2}f}{\partial \sigma ^{2}}\right]$ is discussed, and applied to Schubauer's measurements of a flow round an elliptic cylinder. Two methods of step-by-step integration are indicated. The separation point is found by approaching it from downstream of separation; and in the second approximation its position is at x=2$\cdot $00 as against Schubauer's value x=1$\cdot $99. It is also shown that in order that physical separation (without singularities) may take place, the curve of velocity u(x) outside the boundary layer must have a point of inflexion. The equation is approximately integrated from the position of minimum pressure, and compared with Hartree's results. The equation is approximately integrated downstream of separation for a certain distance, and the evaluated velocities are compared with the observed values.