The historian of technology should be ready to use all these sources, and to name upon the talents of the archaeologist, the engineer, the architect, and other specialists as applicable. The sense of social need have to be strongly felt, or people will not be prepared to devote resources to a technological innovation. The thing needed may be a more environment friendly cutting software, a more powerful lifting system, a labour-saving machine, or a method of using new fuels or a brand new source of energy. Or, because navy wants have at all times provided a stimulus to technological innovation,…