THE catalogue of the twenty-second Annual Exhibition of Scientific Instruments and Apparatus, held at the Imperial College, South Kensington, on Jan. 5—7 by the Physical and Optical Societies, is an illustrated octavo volume of 160 pages and constitutes a valuable record of the position of scientific and technical instrument making in Great Britain at the present time. Although the number of firms exhibiting was slightly less than last year, the space required for their exhibits was greater, and an additional hall on the lower ground floor of the College was utilised. The circulation of the catalogue a few days before the exhibition opened was of great assistance to those at a distance who wished to purchase apparatus, as it allowed them to see which firms make the apparatus and which stands it was necessary to visit in order to compare their productions. Apparatus not previously exhibited was indicated as usual in the catalogue by an asterisk, but there appears at present to be no sign indicating when new apparatus involves the application of a principle not previously used in that type of apparatus, although there was a number of exhibits to which such a sign might have been attached. The catalogue shows a tendency, which we think should be encouraged, for makers of apparatus to give sectional views and diagrams of electrical connexions instead of pictures of the outsides of the cases containing the apparatus. Present-day purchasers are more likely to be influenced by internal arrangements than by outside appearances. As the exhibits of the firms are given in alphabetical order in the catalogues and the numbering of the stands depends not on the name of the firm but on their position in the exhibition hall, it would save the time of a visitor at a stand, who wishes to turn up in the catalogue the firm exhibiting, if, when the description of the exhibit extends to several pages, the name of the firm appeared either at the head or in the margin of each page.