Ironically, only the prematurely titled Metric Is Here is current enough to mention the recent congressional defeat of U.S. conversion to SI (International System) measurements. Still, assuming that ""some day"" we will have to catch up with the rest of the world, here are three more arguments and aids to ease the conversion. None is as elementary as Branley's Think Metric (KR, 1973) or as amusing as Deming's Metric Power (KR, p. 378, J-172). Donovan's, the most difficult of the lot, is comparable to Hirsch's Meter Means Measure (KR, 1973) in its long history of measurement (from cubits and shekels and tuffets to our extended congressional debate) and in its enthusiasm for the rational system that will save us from present ""chaos,"" aid world harmony and negate the current Communist advantage in the race to conquer both space and third world sympathy. Like Donovan, Stover also covers centuries of measurement history and associates Sputnik with Russia's metric conversion, and ail three of the present books explain metric units and standards and metric/ customary equivalents and survey the projected effects of our changeover. Here Donovan is most vigorous, classifying different industries according to the extent of impact and assigning arithmetic exercises along the way (the cooking complications are enough to convert you to take out foods). Stover is less imposing, with linear, mass, temperature and other equivalency tables and some elementary metric arithmetic, and Moore most helpful on a practical level, arranging his tables according to the area -- drugstore, workshop, kitchen, etc. -- where they will most commonly be applied and offering specific hints for dealing with the transition period. In all, though we find the cumulative arguments irresistible, we can't help wondering why not one of the six introductions we've read so far gives any consideration to American engineers' reluctance to make the change, to the handiness of cups, tablespoons, feet and yards, or to any possible points for the other side.