ALTHOUGH the report of the Lubrication Committee has not yet been issued, a “Memorandum on Solid Lubricants,” prepared for the Committee by one of its members, Mr. T. C. Thomsen, has recently been published (Bulletin No. 4 of the Department of Scientific and Industrial Research Advisory Council). This pamphlet of twenty-eight pages contains a digest of the existing knowledge in this branch of the subject, and will be found most useful to all engineers and users of machinery. The solid lubricants referred to are natural and artificial graphite (which are by far the most important), talc, mica, and such substances as flowers of sulphur, white lead, etc., which are occasionally used for curing hot bearings. The greater part of the bulletin is concerned with graphite, and although there is not much matter which is new, there isi a great deal of information which will be of interest to many users of lubricants. The action of solid lubricants and the conditions under which they can be usefully employed are clearly explained.