This book is written for those who are not earth scientists and is a valuable addition to the Scientific American series. The chapters, written by scientists, were first published as articles in the Scientific American magazine and form here a composite of geophysical knowledge up to this time. Since our planet may be considered as a series of concentric spheres, the sections of the book are divided accordingly -- the lithosphere (articles on the earth's interior, crust, heat); the hydrosphere (circulation of the oceans, glacier masses); and the atmosphere (its circulation, the ionosphere). Included too, are articles on ""The Origin of the Earth"", at best, a matter of greater or less probability, in which theories and their likelihood are discussed, and ""The Satellite Project"" of the International Geophysical Year is explained. This compact volume, addressed to the layman, is worthwhile.