Where does invention end, and design begin?

Abstract

A technical product does not come about by a continuous process—it evolves through separate and clearly distinguishable stages. The first of these starts with the realization that a certain device or machine is needed—let us say, for example, a machine for converting the available energy of water into work at the rotating output shaft of an engine. First we must be clear in our minds what physical principle is to be employed in the solution of the problem. In the example just mentioned the energy can be transferred by allowing the water either to rotate the shaft by means of suitably-shaped blading (the water-turbine) or to displace the piston of a reciprocating engine and produce the rotation by a crank mechanism.