Yet, were our sea frontier as strong as it now is weak, passive self-defence, whether in trade or war, would be but a poor policy, so long as this world continues to be one of struggle and vicissitude.  All around us now is strife; “the struggle of life,” “the race of life,” are phrases so familiar that we do not feel their significance till we stop to think about them.  Everywhere nation is arrayed against nation; our own no less than others.  What is our protective system but an organized warfare?  In carrying it on, it is true, we have only to use certain procedures which all states now concede to be a legal exercise of the national power, even though injurious to themselves.  It is lawful, they say, to do what we will with our own.  Are our people, however, so unaggressive that they are likely not to want their own way in matters where their interests turn on points of disputed right, or so little sensitive as to submit quietly to encroachment by others, in quarters where they long have considered their own influence should prevail?

Our self-imposed isolation in the matter of markets, and the decline of our shipping interest in the last thirty years, have coincided singularly with an actual remoteness of this continent from the life of the rest of the world.  The writer has before him a map of the North and South Atlantic oceans, showing the direction of the principal trade routes and the proportion of tonnage passing over each; and it is curious to note what deserted regions, comparatively, are the Gulf of Mexico, the Caribbean Sea, and the adjoining countries and islands.  A broad band stretches from our northern Atlantic coast to the English Channel; another as broad from the British Islands to the East, through the Mediterranean and Red Sea, overflowing the borders of the latter in order to express the volume of trade.  Around either cape—­Good Hope and Horn—­pass strips of about one-fourth this width, joining near the equator, midway between Africa and South America.  From the West Indies issues a thread, indicating the present commerce of Great Britain with a region which once, in the Napoleonic wars, embraced one-fourth of the whole trade of the Empire.  The significance is unmistakable:  Europe has now little mercantile interest in the Caribbean Sea.

When the Isthmus is pierced, this isolation will pass away, and with it the indifference of foreign nations.  From wheresoever they come and whithersoever they afterward go, all ships that use the canal will pass through the Caribbean.  Whatever the effect produced upon the prosperity of the adjacent continent and islands by the thousand wants attendant upon maritime activity, around such a focus of trade will centre large commercial and political interests.  To protect and develop its own, each nation will seek points of support and means of influence in a quarter where the United States always has been jealously sensitive to the intrusion of European powers.  The precise