The object of a study of physical measurements is to develop the thinkingand reasoning powers, to furnish the special kinds of mental tools, and todevelop the special kind of mental attitude that result from properlymaking and analyzing various kinds of measurements with particularregard to their precision and accuracy. The special attitude referred to isthe full, operating realization that accuracy itself can be made a subjectof measurement, that there are relative degrees of accuracy, that accuracyis important in one place and means only a waste of effort in another, thatabsolute accuracy is an impossibility, and that a measurement by itselfis of much less value than when accompanied by a statement of its precision.