**Second of the Let's Find Out science series- and gauged a little higher on the age level, but equally successful in content and presentation of somewhat more difficult concepts, scientifically speaking. The authors have been able to simplify the basic principles of moving things,- drag, lift, roll; the basic principles of friction,- levers, inclined planes, rollers, wheels, ball bearings. There are quantities of experiments which even beginning readers can work out for themselves, experiments using home and kitchen supplies such as blocks of wood, rubber bands, cotton balls, soap, screws, pencils, cans, marbles -- things every household can supply. There's a picture quiz which is a novel way of applying acquired information. The text is humorous and entertaining at the same time factually sound. Bill Ballantine's pictures are accurate and decorative. An excellent choice for fact-finding small boys.