The instrument described, known as a `Vane', works on this principle: a system of blades or `vanes' at the end of a rod is inserted into the soil and the torque required to cause the soil to fail under the stresses exerted by the vanes is measured. For soils of high clay content there is a linear relationship between torque and compressive strength. A simple theory is given for the instrument accounting for torque in terms of cohesion and angle of internal friction. The theory is in good agreement with experiment for angles up to at least 10°. The effect on the torque of the rate of rotation of the vanes has been investigated, and it is shown that the behaviour of the Vane is analogous in some respects to that of a Couette viscometer.