The eternal question of the distinction to be drawn, in teaching elementary Mechanics to youngsters, between mass and weight has recently thrust itself upon me in discussing with a Science colleague the choice of a textbook on General Science suitable for pupils, aged about 11 or 12 years, beginning the subject. The first year General Science syllabus which he has drawn up excludes as far as possible all quantitative work, my own Mathematics department is left to deal with the fundamental teaching of all work involving units, not only of mere length, area, and such things as invariably occur in elementary mathematical teaching, but also of such others as temperature and our old friends mass, force, weight, density, and so on, which will in time be used in the Mechanics course for which the Mathematics department assumes responsibility and to which the Science department will refer incidentally as it feels the need.