The conclusion to be drawn is too obvious to be stated. Perhaps the conclusion is not broadly new; but possibly the idea is new that so small a difference in errors made will, under conditions of sufficient difficulty, produce such a tremendous difference in results. Now, a division is more complex and more difficult to handle perfectly than is a battleship; a squadron more so than a division; a fleet more so than a squadron; a navy more so than a fleet. _Necessity for Knowledge of the Naval Machine_.--There is no machine or tool so simple that knowledge of it is not needed in order to use it skilfully. This does not mean that intimate knowledge of the details of construction of a machine is necessary in order to operate it; it does not mean, for instance, that a sharp-shooter must have a profound knowledge of the metallurgy of the metal of which his gun is mainly made, or of the laws of chemistry and physics that apply to powder, or of the laws of ballistics that govern the flight of the bullet to its target. But it does mean that any skilful handler of any machine must know how to use it; that a sharpshooter, for instance, must know how to use his machine--the gun. Of course, a sharpshooter's skill is exercised in operating under very limited conditions, the conditions of shooting; and it does not include necessarily the maintenance of his gun in good condition. The operating of some machines, however, includes the maintenance of those machines; and a simple illustration is that of operating an automobile. An automobile is constructed to be operated at considerable distances from home; and a man whose knowledge and skill were limited to steering, stopping, starting, and backing the car--who had no knowledge of its details of construction and could not repair a trifling injury--would have very little value as a chauffeur. A like remark might truthfully be made about the operation of any complex machine; and the more complex the machine, the more aptly the remark would apply. The chief engineer of any electric plant, of any municipal water-works, of any railroad, of any steamship must have the most profound and intimate knowledge of the details of construction and the method of operation of the machine committed to his charge. Recognition of this fact by the engineering profession is so complete and perfect as to be almost unconscious; and no man whose reasoning faculties had been trained by the exact methods of engineering could forget it for a moment. The whole structure of that noble science rests on facts that have been demonstrated to be facts, and the art rests on actions springing from those facts; and neither the science nor the art would now exist, if machines created by engineering skill had been committed to the charge of men unskilled.