DR. A. E. KENNELLY recently presented a report, from the historical point of view, to the Society for the Promotion of Engineering Education, in regard to the adoption of the M.K.S. (metre-kilogram-second) system of units ("The M.K.S. System of Giorgi as adopted by the International Electrotechnical Commission (I.E.C.) in June 1935"). Dr. Kennelly has done his work well, giving a fair statement of the present position. Unfortunately, physicists and engineers are not yet agreed as to the best system of units to adopt. Many of them are in favour of following Heaviside and completely rationalizing the system of units. Others are more conservative, and think that the change, although saving much arithmetic, would scarcely be worth the labour involved in learning all the relations connecting the new and the old units. The two leading organizations are in agreement that a fourth unit is theoretically necessary to link internationally adopted electrical units with the dynamical units of the M.K.S. system. They agree that this fourth unit may preferably be 'space permeability' taken at the definite numerical value of 10-7 (unrationalized). This report of Dr. Kennelly's can do nothing but good.