was well worth the toll exacted in the form of physical discomfort. [Illustration: THE ALCATRAZ LIGHTHOUSE UNDER CONSTRUCTION. THE ALCATRAZ LIGHTHOUSE COMPLETED. This tower off the Californian coast is one of the latest works of the American Lighthouse Department. It has a range of 21 miles.] As a rule, on a wave-swept rock which only shows itself at short intervals during the day, the preparation of the foundations is not an exacting task. A little paring with chisels and dynamite may be requisite here and there, but invariably the engineer takes the exposed surface as the basis for his work. The sea has eaten away all the soft, friable material in its ceaseless erosion, leaving an excellent foundation to which the superstructure can be keyed to become as solid as the rock itself. When the beacon is to be erected upon a sandy bottom, the engineer’s work becomes more baffling, as he is compelled to carry his underwater work down to a point where a stable foundation may be secured. When the Leasowe lighthouse was built on the sandy Wirral shore, the builders were puzzled by the lack of a suitable foundation for the masonry tower. An ingenious way out of the difficulty was effected. In the vicinity an incoming ship, laden with a cargo of cotton, had gone ashore and had become a total wreck. The cotton was useless for its intended purpose, so the bales were salvaged and dumped into the sand at the point where the lighthouse was to be erected. The fleecy mass settled into the sand, and under compression became as solid as a rock, while its permanency was assured by its complete submersion. The stability of this strange foundation may be gathered from the fact that the tower erected thereon stood, and shed its welcome light regularly every night, for about a century and a half, only being extinguished two or three years ago as it was no longer required. In the Old World, and, indeed, in the great majority of instances, the lighthouse is what is described as a “monolithic structure,” being built of courses of masonry, the blocks of which are dovetailed together not only laterally, but also perpendicularly, so that, when completed, the tower comprises a solid mass with each stone jointed to its fellow on four or five of its six sides. This method was first tried in connection with the Hanois lighthouse, off the Guernsey coast, and was found so successful that it has been adopted universally in all lighthouses which are exposed to the action of the waves.