The positions which are indicated on the map by the dark squares have been selected, therefore, upon these considerations, after a careful study of the inherent advantages of the various ports and coast-lines of the Caribbean Sea and the Gulf. It is by no means meant that there are not others which possess merits of various kinds; or that those indicated, and to be named, exhaust the strategic possibilities of the region under examination. But there are qualifying circumstances of degree in particular cases; and a certain regard must be had to political conditions, which may be said to a great extent to neutralize some positions. Some, too, are excluded because overshadowed by others so near and so strong as practically to embrace them, when under the same political tenure. Moreover, it is a commonplace of strategy that passive positions, fortified places, however strong, although indispensable as supports to military operations, should not be held in great number. To do so wastes force. Similarly, in the study of a field of maritime operations, the number of available positions, whose relative and combined influence upon the whole is to be considered, should be narrowed, by a process of gradual elimination, to those clearly essential and representative. To embrace more confuses the attention, wastes mental force, and is a hindrance to correct appreciation. The rejection of details, where permissible, and understandingly done, facilitates comprehension, which is baffled by a multiplication of minutiae, just as the impression of a work of art, or of a story, is lost amid a multiplicity of figures or of actors. The investigation precedent to formulation of ideas must be close and minute, but that done, the unbiassed selection of the most important, expressed graphically by a few lines and a few dots, leads most certainly to the comprehension of decisive relations in a military field of action.