Like most inventions, Blueprinting developed out of necessity - the need to reproduce small quantities of drawings quickly and cost effectively. Before its discovery, construction was an extremely slow process - there was only one set of drawings to work from. Although prints could be made through traditional printing methods, the high cost involved made doing so impractical. Today, blueprints can be made so cheaply that every worker on a job can have a set. The development of Blueprinting has gone hand-in-hand with the tremendous growth of industry during the twentieth century. Not much has been written about its discovery, but most authorities agree that Blueprinting can be credited to the English astronomer and scientist, Sir John Frederick Herchel. In 1837, Herchel discovered that light created reverse images on paper that had been coated with silver chloride. After experimenting with various chemicals, Herchel made a "blue print" of the design for his observatory's telescope. The process quickly spread to France, Germany and Switzerland where improvements were made to its practical application. It was not introduced to the United States until 1876, when the Swiss displayed the technology at the Philadelphia Centennial Exposition. Information taken in parts from "The Development and Practice of Blue Printing and Allied Processes" by James Ashton Greig.