"Tidal waves are probably accountable for some unexplained losses. There are three classes of such waves--those due to submarine seismical disturbances, solitary waves occurring in an otherwise calm sea (the origin of which is obscure), and cyclonic waves. Each is very dangerous, the first and last chiefly in the vicinity of coasts, the second out at sea. It was a seismic wave which wrought such havoc at Lisbon in 1755 and in Japan in 1896, when 30,000 people were killed. But the effects of these do not usually extend far out to sea, as do those of solitary waves. Many records of the latter have been given where the decks of vessels have been swept of all hands and of all deck erections. In 1881 all hands were washed off the decks of the _Rosario_. In 1882 the master and half the crew of the _Loch Torridon_ were swept off the deck by a tidal wave. In 1887 the _Umbria_ was flooded by two great waves. In 1894 the _Normania_ was struck by a solid wall of water reaching as high as the bridge, smashing the cabin on the promenade deck, and carrying away the music room and the officers' quarters. The height of tidal waves ranges from forty to eighty feet. The Cunarder _Etruria_ was struck by a tidal wave on the 10th of October, 1903, when a Canadian gentleman was killed and several wounded. The captain's port bridge and stanchions were carried away. Though such waves would not greatly endanger the huge modern liners, they might have swamped their predecessors by breaking through the decks or rushing down hatchways and skylights. Many vessels have been lost by being pooped by vast storm waves, which are not as high as many tidal waves. "In reference to mysterious agencies, these can be dismissed in the present state of knowledge. The secrets of the sea have been investigated so well that no destructive agent is likely to exist that is not known to science. Collision with a whale would not damage a liner, though it would be bad for the whale. The sea serpent may be dismissed without comment. The eruption of submarine volcanoes may be dangerous to small vessels, but the idea of harm from them can not be entertained in connection with the Atlantic service. So that, after all, we are driven back for the solution of these disappearances to the same causes which are known to have wrecked so many vessels. Among these must be included collision with derelict wrecks, which have been known to drift about in the Atlantic for over a twelvemonth, and unhappily the malicious placing of explosives among the cargoes of liners, as was done at Bremerhaven in 1875."