The measurement of electric stresses in liquids using the electro-optic Kerr effect has been restricted to polar liquids with high Kerr electro-optic constants. A new high-speed ellipsometer has been built for the measurement of small degrees of Kerr-effect ellipticity in an electrically stressed non-polar liquid. The new instrument employs electro-optic crystals and has a response time of the order of a millisecond.