as they could clutch, the men dashed into the water with paeans and shouts and the broken pitchers of fallen Jericho.  The violet phosphorescence lighted them on their way, and tracked with luminous curve and star every move of the enemy.  The gashed water at every stroke of club or swish of tail or fin bled in blue and red fire, as if the very sea was wounded.  The enemy’s line of battle was broken and scattered, but not until more than one of the assailants had looked point-blank into the angry eyes of a shark and beaten it off with actual blows.  It was the Thermopylae of sharkdom, with numbers reversed—­a Red Sea passage resonant with psalms of victory.

There are novel difficulties as well as dangers to be encountered.  The native courage of the man must be tempered, ground and polished.  On land it is the massing of numbers that accomplishes the result—­the accumulation of vital forces and intelligence upon the objective point.  The innumerable threads of individual enterprise, like the twist of a Manton barrel, give the toughest tensile power.  Under the sea, however, it is often the strength of the single thread, the wit of the individual pitted against the solid impregnability of the elements, the vis inertiae of the sea.  It looks as if uneducated Nature built her rude fastnesses and rocky battlements with a special view to resistance, making the fickle and unstable her strongest barricade.  An example of the skill and address necessary to conquer obstacles of the latter kind was illustrated in Mobile Bay.  There lay about a sunken vessel an impenetrable mail of quicksand.  It became necessary to sink piles into this material.  The obstacle does not lie in its fickle, unstable character, but its elastic tension.  It swallows a nail or a beam by slow, serpent-like deglutition.  It is hungry, insatiable, impenetrable.  Try to force it, to drive down a pile by direct force:  it resists.  The mallet is struck back by reverberating elasticity with an equal force, and the huge pointed stake rebounds.  Brute force beats and beats in vain.  The fickle sand will not be driven—­no, not an inch.

Wit comes in where weight breaks down.  A force-pump, a common old-style fire-engine, was rigged up, the nozzle and hose bound to a huge pile,

          to equal which the tallest pine
  Hewn on Norwegian hills, to be the mast
  Of some great ammiral, were but a wand.

The pump was set to work.  The water tore through the nostril-pipe, boring a hole with such rapidity that the tall beam dropped into the socket with startling suddenness.  Still breathing torrents, the pipe was withdrawn:  the clutching sand seized, grappled the stake.  It is cemented in.

  You may break, you may shatter the stake, if you will,

but—­you can never pull it out.