Time after time the engineers have sought to subjugate this danger, but without avail. The sea-bed is so soft and absorbing that a firm foundation for a tower defies discovery. One brilliant attempt was made to sink a caisson, similar to that employed for the famous Rothersand light in the River Weser. The mammoth structure was built, and with extreme difficulty was towed out to the selected site. But the seas roared against this attempt to deprive them of their prey. They bore down upon the caisson and smashed it to fragments, causing the engineers to retire from the scene thoroughly discomfited. When a huge mass, weighing several hundred tons, could be broken up by the maddened seas so easily, of what avail were the knowledge and effort of man? The Diamond Shoals still resist conquest. The only means of warning ships of their presence is a lightship moored well out beyond the pale of their sucking embrace. At the present time the United States Lighthouse Board mounts guard over 17,695 miles of coastline. This aggregate embraces, not only the two seaboards of the North American continent, but sections of the Great Lakes, the Philippines, Alaska, Hawaiian Islands, and the American Samoan Islands, the total detailed coast or channel line being no less than 48,881 miles. In order to guide the mariner on his way through waters over which the Stars and Stripes wave, no less than 12,150 lights of all descriptions are required, demanding the services of an army of 5,582 men and women; while the cost of maintenance exceeds £1,200,000, or $6,000,000, per annum. Seeing that the country levies no tolls for services rendered in this connection, the shipping community, and humanity in general, owe a deep debt of gratitude to a powerful nation. The United States share with Great Britain, Austria, Belgium, Spain, France, Italy, the Netherlands, and Sweden, the expense of maintaining a lighthouse which is situate on the property of none of them. This is a kind of no man’s, and yet it is every man’s, light. The beacon is not located in an out-of-the-way part of the world, such as the Arctic Sea, as might be supposed, but mounts guard over one of the busiest marine thoroughfares of the globe--the western entrance to the Mediterranean. This unique light is that of Cape Spartel, on the Moroccan coast. While it was built at the expense of Morocco, the responsibility for its maintenance was assumed by the foregoing Powers, in accordance with the convention of March 12, 1867, which has remained in force since. There is no other light upon the seven seas which has so many Powers concerned in its welfare and maintenance. CHAPTER XVI THE LAMP-POSTS OF THE GREAT LAKES OF NORTH AMERICA