This book by Mr Glegg on the principles of the design process is concerned with carrying out the scientific research needed to obtain data for engineering design. He discusses the various kinds of experiments THAT are appropriate to particular situations and which are likely to yield the required data at minimum cost. Mr Glegg's objectives are essentially practical and he aims to help the designer, who often tends to become a specialist when he ought to be a general practitioner, to think through a research problem, even in an area totally outside the range of his previous experience. As in Mr Glegg's previous books, the principles are illustrated and brought home by further, often entertaining, examples from his wide range of experience as an inventor, consulting engineer, director of research and company director.