It is obvious that the more complicated in construction any machine is, the more time and study are needed to understand it fully; and that the more complicated its method of operation is, the more practice is needed in order to attain skill in operating it. The more simple the method of operation, the more closely a machine approaches automatism; but even automatic machines are automatic only in so far as their internal mechanisms are concerned; and the fact of their being automatic does not eliminate the necessity for skill in using them. An automatic gun, for instance, no matter how perfectly automatically it discharges bullets, may be fired at an advancing enemy skilfully or unskilfully, effectively or ineffectively. In operating some machines, such as a soldier's rifle, or a billiard cue, the number of mental, nervous, and muscular operations is apparently very few; yet every physician knows that the number is very great indeed, and the operations extremely complex--complex beyond the knowledge of the psychologist, physicist, chemist, and biologist. The operation of more complex mechanisms, such as automobiles, seems to be more difficult, because the operator has more different kinds of things to do. Yet that it is really more difficult may be doubted for two reasons; one being that each single operation is of a more simple nature, and the other reason being that we know that a much higher degree of skill is possessed by a great billiardist than by an automobile chauffeur. Of course, the reason of this may be that competition among billiardists has been much more keen than among chauffeurs; but even if this be true, it reminds us that _the difficulty of operating any machine depends on the degree of skill exacted_. It also reminds us that, if a machine is to be operated in competition with another machine, the skill of the operator should be as great as it can be made. The steaming competitions that have been carried on in our navy for several years are examples on a large scale of competitive trials of skill in operating machines. These machines are very powerful, very complex, very important; and that supreme skill shall be used in operating them is very important too. For this reason, every man in the engineering department of every ship, from the chief engineer himself to the youngest coal-passer, is made to pass an examination of some kind, in order that no man may be put into any position for which he is unfit, and no man advanced to any position until he has shown himself qualified for it, both by performance in the grade from which he seeks to rise, and by passing a professional examination as to the duties in the grade to which he desires to rise.