The youngest readers in this age group should find no difficulty in grasping the elementary principles of mechanics which are introduced in words and pictures. Mrs. Pine and Mr. Levine have provided a text which is very direct and to the point as they explain the lever, the inclined plane, the pulley, the screw, etc. Each is described for function and practical application with suggestions for easy experiments and a short list of familiar tools embodying these basic principles and which trades make use of them. The illustrator's pictures are good natured, plain and square with the machine or tool under discussion done in a hard-to-miss solid black. Teachers involved in early grade accelerated math programs are always on the lookout for this sort of simple, conceptual material.