How are matches made? Why is dry cleaning called dry? How does a speedometer work? Why can the heat of an iron be regulated? What makes a ship float? Why does a zipper zip? Diagrams and drawings accompany a page of explanatory text for each of the 1071 entries which explain the principles of why things work. Many of the explanations are beyond the understanding of elementary school students, but the answers to many of their inquiries as to how things work are to be found easily by the curious boy or girl. Much more comprehensive in scope than Mann's How Things Work (Crowell, 1960) but not as useful for the general reader.