An important revelation of the war is the smoothness and rapidity with which large bodies of troops, with all their impedimenta--horses, artillery, etc.--have been transported by water. This has, of course, been possible only for Great Britain and her allies, and for them only because they have held unchallenged the command of the sea. It is thus, first of all, a confirmation of the lesson with which this paper opened--the lesson that command of the sea is a factor of the very first importance in any war in which it is a factor at all. It is secondarily a lesson in the ease with which a nation which has command of the sea can, in these days of large fast steamers, transport its military forces in practically unlimited numbers to any distance that may be desired. It is thus an answer to the protestations of those who insist that the United States is secured against the danger of invasion by the thousands of miles of water which separate its coasts from those of possible enemies; for it demonstrates what has, from the day of the first Atlantic crossing by a steamship, become more and more notably a fact--that the oceans which separate frontiers for certain purposes, connect them for other purposes and especially for purposes of transit and transportation. The term "Ocean Highway" is no mere figure of speech. The millions of troops that have passed by water from England into France have made the passage with infinitely less difficulty than has been connected with the further passage by land to the fighting lines; and the hundreds of thousands from England, France, India, and Australia, which have assembled in the Near East could not have covered the distances that they have covered, if they had moved by land, in ten times the number of days they have occupied in moving by sea. The sea being clear of enemy ships, the route from Liverpool to the Dardanelles has been a lane for an easy and pleasant promenade. With the Atlantic and Pacific controlled by the fleets of nations at war with us, their waters would invite, rather than impede, the movement of an army to our shores. It would be difficult to exaggerate the significance of this lesson for the United States.