In making simplifying assumptions in order to arrive at general truths, the authors are following the practice of pure science. In the laboratory one may use what ever simplifications may be needed for separating out the factors of complex phenomena, but in applying ascertained truths to works practice one realizes that industrial processes start with a complexity which is always much greater than could be permitted in a laboratory experiment devised with the Object of arriving at a clear answer to a simple question. The book is intended especially for those who are interested in ingots and engaged in making them, and such persons may be expected to read it critically.