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.

The same principles apply to all machines; and the common sense of mankind appreciates them, even if the machines are of the human type.  A captain of a company of soldiers, in all armies and in all times, has been trained to handle a specific human machine; so has the captain of a football team, so has the rector of a church.  The training that each person receives gives him such a subconscious sense of the weights and uses of the various parts of the machine, that he handles them almost automatically—­and not only automatically but instantly.  The captain on the bridge, when an emergency confronts him, gives the appropriate order instantly.

Now the word “machine” conveys to the minds of most of us the image of an engine made of metal, the parts of which are moved by some force, such as the expansive force of steam.  But machines were in use long before the steam-engine came, and one of the earliest known to man was man himself—­the most perfect machine known to him now, and one of the most complicated and misused; for who of us does not know of some human machine of the most excellent type, that has been ruined by the ignorance or negligence of the man to whose care it was committed?