Tales of dramatic change in cotton textile production often begin the story of the British Industrial Revolution of the late 18th century. The textile revolution has provided economic historians with powerful symbols of the entire process of industrialization-the new machinery, the steam engine, and the “dark satanic mills” which housed them-but these innovations are not merely symbolic. They profoundly affected regional if not national economies, led to substantial increases in labor and capital productivity over the course of a century, and contributed to an early phase of modern economic growth. It is thus important to our study of what we call the Industrial Revolution that we continue to characterize, measure, and explain the impact of changes in production technologies. This should apply as much to the central symbolic industry of textiles as to other and perhaps more important sectors. In the story of the cotton industry, references to the new machinery usually emphasize the large productivity effects of the water frame and the spinning mule, and nod in the direction of Cartwright’s power-loom, all of which were late lSth-century devices. To be sure, the spinning inventions were important, but further development of spinning technology was embodied in a series of modifications whose cumulative impact was at least as significant as the adoption of the original machines (cf. Rosenberg, 1976). Cartwright’s powerloom, by contrast, was little more than a flash in the pan; it was not until after 1815 that powerlooms (of different design) began to play more than a negligible role in cotton weaving, and it was not until the 1850s that weaving by machine triumphed over the alternative, traditional subsector of handloom weaving. Over these years, in a pattern similar to that of spinning, power-loom technology was modified