A rapid and accurate method of determining the density of a mineral has long been sought for by mineralogists and gemmologists. The hydrostatic method gives a high degreeof accuracy, but has the drawback that each estimation occupies about a quarter of an hour so that if some ten to twenty specimens have to be investigated the time taken will be considerable. The use of heavy fluids is rapid, but for finer distinctions a large number of fluids is required and they tend, either from evaporation or chemical change, to become variable, while the Westphai balance is only reliable for fairly large portions of the mineral. Several attempts therefore have been made to develop a balance which will give a direct reading. Most of these such as the Kratschner balance have been based upon Leonardo da Vinci's principle of the bent lever, but generally have not been sufficiently delicate or accurate for small specimens.