ALL about the pond the woodland folk are enjoying shore dinners, for it is the time of ebb tide, and a wonderfully low ebb at that. Not for a score of years do I recall such low water. Where, on the ebb of ordinary years, the crow has been able to find one freshwater clam, he may now feed till he can hold no more, for the drought has been long and severe, and the pond has been drained to the very dregs.

I say fresh-water clams, for that is the name commonly applied to the creatures, though I know that I might more properly call them river mussels, and if I wished to be severely scientific I should say Unio margaritifera, though it is difficult to be sure of your margaritifera, as there are about fifteen hundred species of unios known to people who classify creatures, and most of these are found in the rivers of this country.

Little do the crows care for that. In the sunny coves they have their clambakes, and as I slip slyly up I fancy I hear them smack their mandibles. As I round the screen of shore-loving button bushes, I know I shall come upon them, and I expect to find them seated in riotous fellowship, with napkins spread across broad waistcoats, dipping delicious mouthfuls in melted butter and tucking them away behind the white napkins. I have always missed the napkins and the butter dishes, but the shells are proof enough of what has been going on. If the mother crow carries the table furnishings away with her when she flies, that is no more than human picnickers do when driven from the sea beach.

The pond when full is ten feet deeper than it is now. In May the water lapped the forest roots on its edges; now from the forest to the mud of the very bottom where still the water lingers a strip of slanting beach stretches for a hundred yards. The crows are not the only creatures which have made tracks on this. Close by the edge in the soft mud the heron has walked with dignity, leaving footmarks that proceed precisely: The heron may not have large ambitions, but he is purposeful and does not turn aside. The crows gurgled and ha-haed over their clambake; the heron takes his fish course as solemnly as if he were taking the pledge.

All along you will see where the squirrels have come down to drink, skipping vivaciously, taking a sip here, bouncing away to examine something there, remembering that they came for a drink after all and taking a good one, then hurrying back with long leaps in a straight line for the trees. The squirrel is not solemn, far from it, -- but he is business-like, and though there is humorous good fellowship in his every hop, he nevertheless does not linger long from his work.

Very different from this is the track of mister skunk. He wanders aimlessly along, often as much sidewise as straight ahead. The skunk doesn't know where he is going and he isn't even on his way. I never see his tracks, whether on the pond shore or elsewhere, but I renew my doubts as to his habits. He is out much too late at night. His tracks show it. I think he had his drink before  he came to the water. Probably he too knows how toothsome are the unios and is searching for them in his maudlin fashion.

Then there are the muskrats. They do not have to wait for their clam banquets till the water is low. They are expert divers and gather the unios at such times as suit their fancy. You will see their tracks in regular runways in the shallow water of the muddy coves, whence they are apt to follow some trickling streamlet to the bank where the summer burrows are at high water.

Later, along the marshy edges you will find their winter teepees, piled to conical heights with sods and roots, with a warm refuge above the ice and an exit below, whence they may swim in search of food. The tracks of the muskrats show every mark of the industrious villager. They stick close to well-traveled paths, and though the muskrats are out nights no one would for a moment question their temperance and industry. Their characters are excellent ones, beyond suspicion, and their tracks show it.

On the pond shore at ebb tide the glaciers, too, have left their tracks, though it is probably several hundred thousand years since any have been this way. Where there are granite ledges you may know that these were here before even the glaciers stalked solemnly by, for they show where the ice in grumbling grandeur ground small stones against them and gradually wore out ruts in the enduring granite by force of attrition.

The track of the glacier is like the trail of the serpent, -- it leaves no toe-marks, but its sliding progress is unmistakable. Side by side with the ledge which shows these striae you may see on the soft mud imprints of this year's leaves, dropped a moment there by the wind, then whirled away again, but leaving their tracks behind them. This mark of the season may be obliterated by a breath, or it may be covered with sifting silt and finally harden into sandstone and bear the trail of the leaf as far down the ages as has come that of the glacier. Here are moments and aeons elbowing one another for place.

Other interesting records of past time may be read in Stumpy Cove, which is still the wildest and most secluded of spots, though the trolley tripper has found the pond and builds his bungalows on its shore, sinks his tin cans in its waters, and scares the bullfrogs with his phonograph. The tin cans will not last long, however. Fresh water in motion is continually giving up oxygen, and this with the humic acid of the mud bottom will soon scatter these disfigurations in scales of brown oxide. But all these solvent forces, acting through two centuries, have had little effect on the stumps of Stumpy Cove.

The skunk doesn't know where he is going and he isn't even on his way 

The heart-wood is still sound, their interlaced roots tell the story of what happened on the spot in the rich muck of the swamp, as Stumpy Cove was then, before Myles Standish had set foot on Plymouth Rock or the first white man had spied inland from the summit of Blue Hill. For the pond as it is now is only about a hundred years old. For a hundred years before that it was a meadow, flowed occasionally by the farmers of the region about it.

Before that Stumpy Cove was a great white-cedar swamp and the great white cedars stood in it, two feet in diameter, their clean straight trunks running up fifty feet or more without a knob or limb. This natural meadow with hay for their cattle for the cutting, these cedar swamps with their century-old growth, were what attracted the first settlers to this region, and hardly had the dawn of the sixteenth century come over the Blue Hills before their axes were at work in Stumpy Cove and similar swamps all about, getting out shingle stuff for the Boston market. But whereas in all the other swamps the young cedars were allowed to grow in again for succeeding generations of woodsmen, here new conditions arose.

The meadow was flowed intermittently for a century; then the pond grew out of it. Not only might no seedlings find roothold there, but the very black muck in which they might grow was washed away from the roots of the great stumps. These, in the main, have endured, losing their bark and sap-wood, but with the heart-wood still firm after the lapse of two centuries.

Here at this ebb tide I read the record of growth of trees that had their beginnings more than three centuries ago. These roots so twine and intertwine that the original sap, drawn from the tender tips, must have nourished any one of several trees indifferently, for heart-wood joins heart-wood in scores of places near the stump and far from it, showing that each tree stood not only on its own roots, but on those of its neighbors all about it; not only was it nourished by its own rootlets, but by those of trees near by. No gale could uproot these swamp cedars. United they stood and divided they might not fall. It is a curious method of growth, and I dare say it obtains in many swamps where the white cedars stand close, but under no other circumstances could it have been revealed to me, casually strolling that way three centuries after it happened.

At high water all these curious roots are submerged and you see only the butts of the trees, numerous miniature islands on which many an alien growth has made port. Here in June the dour and melancholy cassandra disputes the footing of the wild rose, and the huckleberry and sweet-fern twine in loving companionship, afloat as ashore. Here intertwine the sheep laurel and the hardhack, the meadow-sweet and the marsh St. John's-wort, garlanding the white skeletons of the ancient trees and making them young again with the odorous promises of spring.

In midsummer, among patches of green and gray moss, you will find tiny, diamond-like globules glistening. These are the clear, dew-like drops of glutinous liquid which gem the leaves of the Drosera, northern representative of the Venus's fly-trap. This, the Dionaea, catches flies by means of a steel-trap leaf which closes on them when they light on it. This other, the Drosera, is not so active. It attracts insects with its honey dew, holds them with sticky glands, and grips them, little by little, with bristles. It is a curious and beautiful little plant, and one would hardly think it carnivorous to see it adding its diamond ornaments to the floral decorations which beautify the ancient stumps all summer long.

Yet of all the life histories revealed by the pond at low tide I still think that of the Uniondae the most interesting. You find them all along above and below the margin of the shallow water, their shells most wonderfully streaked with olive-green and pale-yellow in alternate bands, till one might think he had found nodules of malachite which the long-ago glacier had culled from some Labrador ledge and ground to unsymmetrical ovoids before it dropped them on the old-time meadow marge. In certain individuals and certain lights the shells of these obscure creatures send out gleams of green and gold, like gems that have soft fires within them. It is as if an opalescent soul dwelt within, and the thin shell which a crow with his bill may puncture with a blow was so constructed as to hold in the reds and blues of the opalescence, but transmit the greens and gold.

You find many with only the backs of their shells sticking out of the mud. This may be the creature's natural position, but I find far more of them lying quietly on their sides in the shallow water, rocking gently to and fro in the placid undulations as if they were there but to show me their shining colors. But if you watch one intently for a time you will see him open his shell cautiously and put out one foot. This is his best, for it is all he has and he puts it foremost. It is very white and clean, and it might as well be called his tongue, for with it he licks his food. It is half as long as he is, and when he has put it out as far as he can, or as far as he dares, a fine white fringe grows on its outer margin. Thus he gathers in minute animalculae or refuse matter from the surface of the mud, for his stomach's sake.

It is a rather interesting thing to stand by and watch a Unio margaritifera daintily putting away his own particular brand of little necks and mock turtle. At the least untoward sign of interest in the affair, however, he shuts up like a clam, and you will need your pocket-knife if you wish to see more of him.

Where the water is only an inch deep or so over the soft ooze of the bottom you will see where the unio has used this so-called foot as a foot should be used, for he not only stands on it, but walks with its help. These signs are curiously erratic marks drawn as with a sharpened stick for a distance sometimes of yards. If you will inspect the seaward end of this trail you will find a unio in it, generally a young one, for it is he that has left the mark behind him in his travels. For the unio at a certain age is a great traveller; that is, when he is very young. The adults foot it, but the young before they reach their full growth ride, some of them by what you might call the lightning expresses of the pond world.

If you will split a big one at this time of year you will be likely to find within an astonishing number of eggs. These are carried in brood pouches that seem to occupy pretty nearly all the space between the shells. In  seeing them you wonder vaguely where there was room for the bearer of this amazing progeny. Just where they are these young unios grow to maturity of a certain sort, forming minute shells which have hooks, forming also peculiar organs of sense. The hooks and the sense organs are provided that they may not miss that free ride which is the privilege of every young unio if he is to reach the period of adolescence.

At the moment of being sent forth from the home shell the golchidium, for that is what the scientific men call the unio at this stage of the affair, begins to hunt, aided by his sense organs, for a thoroughfare. Here he takes the first conveyance, whether the slow coach of the sluggish horn-pout, the bream automobile, or the pickerel flying-machine. To the first fish that comes by he attaches himself, oftentimes to the gills, and there he rides and, like most travelers, continues to develop.

By and by, being “finished” by travel, he gets off his vehicle at some convenient station, drops into the mud, and is ready to lecture, or so I fancy it, before any of the unio women's clubs on the world as he has seen it. Not until then does the unio, and then only if he is a margaritifera, begin to accumulate pearls.

By what mystery of sunlight and shallow water the unio has acquired the lucent green and gold of the epidermis of his outer shell I do not know, any more than I know what pigments paint or what naiad fingers hold the brush that paints the gold in the heart or the pinky green in the outer sepals of the waterlily. The two find their sustenance in the same mud.

But even if I could tell this I might well pause in wonder over the beauty of the inner shell of this pulseless creature of the ooze. Perhaps the golchidium, darting back and forth beneath the ripples of the surface during its days of travel, catches the radiant blue of the sky, the rosy flush of dawn, and the glory of the rainbow all shivered together in exultant light to make the nacre of the inner surface of its growing shell. For nowhere else in nature may we find such softness of coloring holding such gleams of azure and of fire. The opal beside it is garish and crude. Mother-of-pearl we call it, for out of the same source is born the gem which may be worth the price of a king's ransom.

The unio is the good girl of the fairy tale, for from its lips fall pearls that confound the divers of the Orient. Not from Ceylon nor Sulu nor the Straits of Sunda nor the Gulf of California have come such pearls of bewildering color and fascinating shapes as have been taken from the river mussels of our American streams. For all I know the shallows of my pond may hold a necklace of such value that its fellow has never yet circled the throat of a queen. If so I hope no one will ever find it out, for an ebb tide such as this comes only once in a score or so of years, and when the next one is here I want still to find the beach beautiful with the green and gold and mother-of-pearl of the unios.