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Some thirty years ago, when the laboratory where I worked needed light alloy castings, success depended on divination carried out by the foreman. This hinged upon the effects of spitting in the crucible, and the results beat any scientific method hollow. About five years later we were using more dependable and repeatable, if less picturesque, criteria. This came about because meantime various theoretically‐minded people had studied various apparently minor and irrelevant matters such as the behaviour of single crystals of aluminium. Some of the personal skill and experience hitherto needed for routine operations now could be delegated; at times even to instruments.
R. A. Fairthorne (Thu,) studied this question.