"We've got to have a base of supplies, or something of that sort," the man declared. "We can't start trekking away into the wilderness at once, without consideration and at least some definite place where we can store a few necessaries and to which we can retreat, in case of need. A camp, and--if possible--a fire, these are our first requisites." Their camp they built (regardless of the protests of birds and squirrels and many little woodland folk) roughly, yet strongly enough to offer protection from the rain, under a thick-leaved oak, which in itself gave shelter. This oak, through whose branches darted many a gay-plumaged bird of species unknown to Stern, grew up along the overhanging face of Spring Rock, as they christened it. By filling in the space between the rock and the bole of the oak with moss and stones, and then by building a heavy lean-to roof of leafy branches, thatched with lashed bundles of marsh-grass, they constructed in two days a fairly comfortable shack, hard by an abundant, never-failing supply of the finest water ever a human set lip to. Here Stern piled fragrant grasses in great quantity for the girl's bed. He himself volunteered to sleep at the doorway, on guard with his only weapon--a jagged boulder lashed with leather thongs to a four-foot heft, even in the; very fashion of the neolithic ancestors of man. Their food supply reverted to such berries and fruits as they could gather in the fringes of the forest, for as yet they dared not penetrate far from the shore. To these they added a plentiful supply of clams, which they dug with sharp sticks, at low tide, far out across the sand-flats--toiling for all the world like two of the identical savages who in the long ago, a thousand or five thousand years before the white man came to America, had left shell-heap middens along the north Atlantic coast. This shell-fish gathering brought the action of the tides to their careful attention. The tide, they found, behaved ire an erratic manner. Instead of two regular flows a day there was but one. And at the ebb more than two miles of beach and sea-bottom lay exposed below the spot where they had landed at the flood. Stern analyzed the probable cause of this phenomenon. "There must be two regular tides," he said, "only they're lost in the far larger flux and reflux caused by the vortex we escaped from. Any marine geyser like that, able to, suck down water enough from the sea to lay bare two miles of beach every day and capable of throwing a column of mist and spray like that across the sky, is worth investing gating. Some day you and I are going to know more about it--a lot more!" And that was truth; but little the engineer suspected how soon, or under what surpassingly strange circus stances, the girl and he were destined to behold once more the workings of that terrible and mighty force.