The ebb discovers a broad space, firm and wellnigh unimpresslonable. The barefooted traveller may walk for miles and be trackless, so tough and elastic the moist sand. It is not an officious thoroughfare, made formal and precise by coarse hands working to plans correct to a hair, but subject to economic deviations of some soulless contractor. It was not laid with the foundation of the earth, and compacted by heat and stress. It is still in the making, and sand, coral, and shell-grit ground to pollen-like fineness and certain chemicals from the reef outside are among its component parts. One other element invokes perpetual thanksgiving--the flaked mica, which glistens delusively with hues of silver and gold, and gives to the tide-swept track that singular pliancy which resists the stamp of passing generations. Midway between high and low water is a zone sensible to the airiest tread, being fitted for such temporary effect by a mechanical operation. Millions of the smallest of crabs, sand-tinted, delicate, apprehensive and alert, possess this area, working out their destiny by digging circular shafts. Obedient agents in the execution of the imperative ordinances of Nature, they have the quality of compacting the almost fluid spoil and carrying it to the surface in pellets complementary to the size of the individual, and such pellets retain their rotundity. They are scattered about, not without design, as may be seen if the industrious workers are closely observed, and in such profusion that the feet of the user of a crab-infested zone must press them flat. Then it is that the track becomes visible as far as the eyes reach. But the incoming wavelets, babbling in unison, dissolve the myriads of laboriously lifted pellets, effacing the record of the passing of man. As the tides ebb, the crabs begin their work again, preparing for the next-coming wayfarer. There is something almost incomprehensively great in the tireless activities of the nervous crabs, for not only do they carry compacted sand from their burrows, but they seem to spend odd moments in forming similar globes from material gathered from the surface. Digging, furrowing the surface in stellate patterns, moulding pellets which to the tenderest ripple are but the plaything of a moment, so are the lives of the shy crustaceans spent. What may be the motive for the perpetual labour, as useless, apparently, as the rolling of Sisyphus's stone? For part of the year the beach is the resort of the red-necked sandpiper, which has an enormous appetite for the small, live things of the sea's margin. To bewilder the birds and so reduce the risk to life, Nature imposes the task upon the crabs of forming replicas of themselves not readily distinguishable in size and tint, which represent labour unconsciously expended as life insurance, and serve the subsidiary purpose of detecting the passing of man.