Economists have long treated technological phenomena as events transpiring inside a black box and, on the whole, have adhered rather strictly to a self-imposed ordinance not to inquire too seriously into what transpires inside that box. The purpose of Professor Rosenberg's work is to break open and examine the contents of the black box. In so doing, a number of important economic problems be powerfully illuminated. The author clearly shows how specific features of individual technologies have shaped a number of variables of great concern to economists: the rate of productivity improvement, the nature of learning processes underlying technological change itself, the speed of technology transfer, and the effectiveness of government policies that are intended to influence technologies in particular ways. The separate chapters of this book reflect a primary concern with some of the distinctive aspects of industrial technologies in the twentieth century, such as the increasing reliance upon science, but also the considerable subtlety and complexity of the dialectic between science and technology. Other concerns include the rapid growth in the development of costs associated with new technologies as well as the difficulty of predicting the eventual performance characteristics of newly emerging technologies.