Thermally induced errors, dominant in a water-tube tiltmeter, are eliminated by using two adjacent tubes containing fluids with densities having different temperature coefficients. Simultaneous measurements of the apparent difference in height between two stations indicated by the two fluids are used to provide the required correction for the density changes. The application of this method could allow precise measurements over long baselines (a resolution of about 10-8 to 10-9 radians in a 1-kilometer instrument) without a level interconnecting tube or deep burial.