changes in the shapes and treatment of his tools, etc. Many of these changes are matters entirely beyond his control, even if he knows what ought to be done.
If the reason is clear to the reader why the rule-of-thumb knowledge obtained by the machinist who is engaged on repeat work cannot possibly compete with the true science of cutting metals, it should be even more apparent why the high-class mechanic, who is called upon to do a great variety of work from day to day, is even less able to compete with this science. The high-class mechanic who does a different kind of work each day, in order to do each job in the quickest time, would need, in addition to a thorough knowledge of the art of cutting metals, a vast knowledge and experience in the quickest way of doing each kind of hand work. And the reader, by calling to mind the gain which was made by Mr. Gilbreth through his motion and time study in laying bricks, will appreciate the great possibilities for quicker methods of doing all kinds of hand work which lie before every tradesman after he has the help which comes from a scientific motion and time study of his work.
For nearly thirty years past, time-study men connected with the management of machine-shops have been devoting their whole time to a scientific motion study, followed by accurate time study, with a stop-watch, of all of the elements connected with the machinist's work. When, therefore, the teachers, who form one section of the management, and who
