AN article by R. W. Paul, published in the November issue of the Journal of Scientific Instruments, is of general interest, as it will help to keep green the memory of the Faraday Centenary Exhibition at the Albert Hall, London, in 1931. He gives excellent descriptions of many of the instruments shown, which illustrate the gradual development of accuracy and quickness in measurement. Ammeters were first made having needles of soft iron polarised by a powerful magnet and having a deflecting coil closely adjacent. In 1881, Ayrton and Perry designed such instruments, the scales being graduated in degrees, which were converted to amperes by the application of a constant. They were the first to use the term ‘ammeter’ instead of amperemeter. It is interesting to remember that Silvanus Thompson strongly discouraged the use of this word, and asked sarcastically why they did not also use the word ‘vometer’ for voltmeter. The Director of the Science Museum has arranged that much of the apparatus shown at the Exhibition will be displayed at the museum from February until May 1932.