The Incas knew more than the (North American) Indians knew but the increasing remoteness of the subjects casts doubt on the viability of this multi-purpose series. In the same third-fourth grade text and tone are disconnected facts about the Incas (identified as Indians who lived in Peru ""hundreds of years ago""), present-day contrasts and a simple project; these are designed either to illustrate a scientific principle (the advantage of a ramp, of fertilizer, the tendency of water to flow downward) or to simulate the practice of the Incas (making a relief map, weaving, building a paved road). Of the former sort, some are so generalized (e.g. fertilizer) as to be suspect; of the latter, only a few (e.g. the quipu for measuring) are actually duplications: weaving a potholder on a ""store-bought loom"" teaches nothing about Inca textiles. The information on Inca techniques is potentially useful for children who are studying the subject in school (if they are studying the subject in school at this level); the projects must be started in school since the instructions are very hazy. A dubious item: teachers may get ideas but kids will get confused.