Great Britain, when she declared war on Germany, did not follow President Lincoln’s example and lay the whole of the German coast under interdict.  Perhaps one reason for this inaction was a desire not unduly to offend neutrals, especially the United States; but the more impelling motive was geographical.  The fact is that a blockade of the German seacoast would accomplish little in the way of keeping materials out of Germany.  A glance at the map of northwestern Europe will make this fact clear.  In the first place the seacoast of Germany is a small affair.  In the North Sea the German coast is a little indentation, not more than two hundred miles long, wedged in between the longer coastlines of Holland and Denmark; in the Baltic it is somewhat more extensive, but the entrances to this sea are so circuitous and treacherous that the suggestion of a blockade here is not a practicable one.  The greatest ports of Germany are located on this little North Sea coastline or on its rivers—­Hamburg and Bremen.  It might therefore be assumed that any nation which successfully blockaded these North Sea ports would have strangled the commerce of Germany.  That is far from being the case.  The point is that the political boundaries of Germany are simply fictions, when economic considerations are involved.  Holland, on the west, and Denmark, on the north, are as much a part of the German transportation system as though these two countries were parts of the German Empire.  Their territories and the territories of Germany are contiguous; the railroad and the canal systems of Germany, Holland, and Denmark are practically one.  Such ports as Rotterdam, Amsterdam, and Copenhagen are just as useful to Germany for purposes of commerce as are Hamburg and Bremen, and, in fact, a special commercial arrangement with Rotterdam has made that city practically a port of Germany since 1868.  These considerations show how ineffective would be a blockade of the German coast which did not also comprehend the coast of Holland and Denmark.  Germany could still conduct her commerce through these neighbouring countries.  And at this point the great difficulty arose.  A blockade is an act of war and can be applied only to a country upon which war has been declared.  Great Britain had declared war on Germany and could therefore legally close her ports; she had not declared war on Holland and Denmark, and therefore could not use the same measure against those friendly countries.  Consequently the blockade was useless to Great Britain; and so, in the first six months of the war, the Admiralty fell back upon the milder system of declaring certain articles contraband of war and seizing ships that were suspected of carrying them to Germany.