A viscometer for liquids of low viscosity was built to be used at temperatures up to ca. 1000°C with the liquid maintained under a vacuum or inert gas atmosphere. The viscometer follows the method first suggested by Helmholz (8) and later successfully developed by Chiong and Andrade (4). In this method, the liquid is enclosed in a sphere; and the sphere is set in rotatory oscillation about a vertical axis. From measurements of the damping of the oscillations and the period and moment of inertia of the rotating pendulum, absolute values of the viscosity are calculated using the equations derived by Chiong and Andrade (4).