AN invention which, apart from its intrinsic merits as a mechanical development, promises to be of especial interest in a scientific sense, is the introduction by a Swiss manufacturer of a range of miniature ball bearings. Ordinary bearings of this class have been made in sizes varying from half an inch to five feet in diameter overall ; but nothing small enough has been available to satisfy the requirements of small and sensitive instruments. The bearings now obtainable as a result of this invention are of several different types and vary in size from 1 to 22 millimetres in diameter overall. They are thus of suitable size for use in such devices as small motors, recorders, meters, clockwork, tachometers and scientific instruments of many kinds in which measured movements are produced by infinitesimal forces, and friction must be eliminated as far aome cases so higs possible. Comparative tests on these bearings and the jewelled bearings they are intended to replace show advantages under three different modes of operation. The time to damp down a rotary motion was in sh as eight times that when plain pivots were used and twenty times that when tapered pivots were used, though there is a good deal of variation in the results. In an oscillatory test the corresponding figures were about 4 and 15, while in the deviation test the results claimed are also favourable. As these new bearings are obtainable at moderate prices, it is probable that, after adequate trials, they will play an important part in the future construction of scientific instruments. They are being marketed by International Technical Developments, Ltd., Thames House, Millbank, London, S.W.I.