It is well, in beginning, to define what we mean by the interchangeable system. We will consider it as the art of producing complete machines or mechanisms, the corresponding parts of which are so nearly alike that any part may be fitted into any of the given mechanisms. So considered, it does not include the manufacture of separate articles, closely like each other, but which do not fit together permanently into a mechanism. If this were meant, the work of the early typefounders would clearly antedate that of the modern manufacturers, as they produced printing types by the process of casting which were similar to each other within very close limits. There is, however, a wide difference between this and the parts in such a mechanism as a gun, for individual types are not permanently articulated. The interchangeable system was developed by gun makers. It is commercially applicable chiefly to articles of a high grade, made in large numbers, and in which interchangeability is desirable. Of the typical articles, such as firearms, bicycles, typewriters, sewing machines, and the like, now produced by the interchangeable system, guns and pistols are the only ones which antedate the system itself. These were used in great numbers, and in military arms especially interchangeability was of the highest value. Under the old system with hand-made muskets, in which each part was fitted to its neighbors, the loss or injury of a single important part put the whole gun out of use until it could be repaired by an expert gunsmith. Eli Whitney, in a letter to the War Department in 1812, stated that the British Government had on hand over 200,000 stands of muskets, partially finished or awaiting repairs.[148] The desirability, therefore, of some system of manufacture by which all the parts could be standardized and interchangeable, was well recognized. There existed a demand for military arms which could meet this condition, but it was felt at the time that it was impossible to meet it. [148] Blake: “History of Hamden, Conn.,” p. 133. The system of interchangeable manufacture is generally considered to be of American origin. In fact, for many years it was known in Europe as the “American System” of manufacture. If priority be assigned to the source which first made it successful, it is American; but the first suggestions of the system came from France. We have already seen that the French mechanics were the first to work upon many of the great mechanical improvements; but here, as in the case of the slide-rest and planer, they seem to have caught the idea only. It was left to others to make it a practical success.