Perhaps they lack that instinctive sense of proportion that some men have--a sense as real as an "ear for music"; or perhaps they lack a willingness or a capability to think about a situation with sufficient intentness to force a clear picture of the situation with all its various features upon the mental retina.
The ability to make a mental picture, be it of a machine, of any group of material objects, such as the various units of a fleet organized as such, or of any other situation, varies with different men; but like every other kind of ability, it can be strengthened by practice, and assisted by appropriate means.

In the engineering arts, the practice is gotten by observing and remembering actual machines; and the assistance is given by drawings of different kinds.
In strategy, the practice is given by observing and remembering the movements of actual fleets; and the assistance by means of drawings of different kinds, and by war problems, and the game-board.

The game-board represents a number of successive pictures, and is not very different in principle from moving-pictures.

In fact, the suggestion has been made repeatedly for several years and is now in process of development that the various situations in tactical games might advantageously be photographed on films and afterward projected in rapid succession on a screen.
One of the curious limitations of the naval game board, both in tactical and strategic games, is that it takes no account of personnel; that it assumes that all the various units are manned by crews that are adequate both in numbers and in training.

Of course, it would be impracticable to test say the relative values of kinds of vessels, unless all the factors of the problem were the same, except the two factors that were competing.