THE Oxford heliometer of 1848 has been placed on exhibition in the Astronomy Collection (Gallery LXIV). This instrument was made for the Radcliffe Observatory, Oxford, by Messrs. A. and G. Repsold of Hamburg on the advice of the famous German astronomer F. W. Bessel, who had in 1838 with a similar instrument obtained the first satisfactory measure of the parallax of a fixed star. The distance of the star, 61 Cygni, was found to be some 400,000 times the sun's distance of 93,000,000 miles. The Oxford heliometer was for many years one of the most powerful and accurate instruments of its kind in the world. It is notable among other things for the first application of electrical illumination to an astronomical instrument. It was dismounted and taken to pieces in 1906, and so remained until its removal in 1935 to the Science Museum, where it has been renovated and set up as it was originally, a striking testimony to the nineteenth century instrument maker's art. In the Chemistry Collection (Gallery LXVI), an original tube of the metal rhodium prepared by its discoverer, Dr. William Hyde Wollaston, about 1825 has been placed on exhibition. Rhodium has recently become of interest as a non-tarnishing substitute for silver in electroplating.