I ALWAYS know the sound of the east wind as it comes over the Blue Hills for the twanging of the bow from which winter has shot his Parthian arrow. The keenest it is in all his quiver of keen darts, for it penetrates joints in one's armor that no gale from Arctic barrens has been able to reach, that no fall of snow or of temperature has weakened. Facing it to-day and feeling its barbs turn in the marrow of my breastbone as I crossed Ponkapoag Pond I began to wonder how it fared with my friends the muskrats who were wintering in the very teeth of it over on the northwest shore. And so I turned my shoulder to the blow and my face to the bog where tepees in a long line spire conically out of the brown grasses on the bog edge, where the pickerel weed flaunted blue banners all summer long.

The thermometer marked a temperature of but a few degrees below freezing, but it was the coldest day of the winter. The bite of the wind off Hudson's Bay is as nothing to the chill which the Arctic sea-water folds in its unfrozen heart as it sweeps from polar depths down the west coast of Greenland, along the Labrador shore, round Newfoundland and down again, shouldering into Massachusetts Day; the reserve corps of the winter's assault, the Old Guard plunging desperately to its Waterloo in the face of all-conquering spring. This chill the east wind had caught up from the green depths of the surges he tossed, and made it the poison of the points which he drove desperately home. Face this wind for a day and you shall feel the venom working long after you have sought shelter, nor shall even the cheer of a big open fire drive it easily from your bones.

Yet you may draw from the chill this cheer, if you will, that no longer is the worst yet to come; it is here and soon the prospect must mend. It seems odd to think that some day next July we shall sniff this frigidity drawn from the depths of the boreal current, borne on the wings of the east wind, and revel in the intoxicating ozone with which it soothes our heat-fevered nostrils.

Over on the bog edge are twenty-seven lodges, built of bog turf and roots, dead grass and rushes, almost any rubbish in fact which Mussascus, as Captain John Smith called him, has been able to get in the neighborhood. Each has a foundation of some sort; one a stump submerged in the muck, another a rude framework of alder sticks which the muskrat cuts with his strong, chisel-like teeth and brings in his mouth as a beaver would: others variously upheld, but all so placed that the entrance may be beneath the water and beneath the ice also, however. thick it may freeze.

Little does the muskrat care for my marrow-piercing east wind. I'll wager that he never knows it blows, for rarely indeed at this time of year does he put his nose out where he might feel it. His stairway leads from the under-water entrance to a cosy and comfortable nest lined with soft grass where he and his fellows cuddle. The mud-smeared, water-soaked material of their walls is frozen to adamant. It is porous enough in spots to give them air for breathing but does not let the cold wind enter. It is as snug and safe a place as any one could devise. An enemy must break through from without and long before he can smash the frozen walls Mussascus has slipped into the water and gone his way beneath the ice, first to another tepee, or if driven from that on again to his burrows in the hard bank a thousand feet away.

Bending my ear close to the nearest lodge I rapped sharply on the rough wall and listened. There was no sound. Again I rapped and my knock was all that disturbed the silence within. Outside the frozen marsh grasses sawed silkily one on another and the frost crystals that the wind was sweeping from the thick white ice shrilled infinitesimally as they slid by, but no sound came from the lodge. Evidently no one was at home. At the next lodge it was different. The rap was succeeded by a second of breathless silence, then there was the sound of scrambling, and as I watched the dark clear ice that always obtains just about the lodge I saw three silver gleams shoot athwart the clear space and vanish under the opaque ice just beyond. Three Mussascuses had fled, their dense, dark, close-set under fur holding the air entangled in its fine fuzz which is impervious to water, thus accounting for the gleam.

Like the fur-seal the muskrat has an outer coat of rather coarse hair and an undervest of much finer, more silky texture. This provides an air space which enfolds him, however long he remains under water, and its chill may not reach him nor can the moisture. Only the soles of his feet and the very tip of his muzzle, the nose-pad, are bare. His ears are set down within his fur, and when he is beneath the surface each holds an earful of it that catches under-water sounds and transmits them as faithfully as it does the sounds of the upper world. He swims by vigorous "dog-paddle" motions of his hind feet, which are large and furnished with stiff, coarse hair that answers for a webbing between the toes. Moreover, these feet are "hung-in" a little in a peculiar club-footed way that makes his gait on land an awkward shamble, but which allows them to "feather" as an oar does in swimming, thus giving his propulsive apparatus the greatest possible efficiency.

People who know Mussascus best differ about the use of his tail. I have never seen him use it except as a very efficient steering oar, but I have been told that he sculls with it as a fish does with his, and thus helps his progress. It is admirably adapted for either purpose, but it is a tail that does not look as if it belonged to any fur-bearing animal. It is almost as long as the muskrat himself and has never a hair from butt to tip. Instead, it is furnished with small stiff scales which might just as well be those of a snake. It is flattened sidewise and trimmed down to almost a knife-edge at top and bottom, and the muskrat uses it most efficiently.

But however well adapted their feet and tails are for swimming and their fur for keeping them warm and dry beneath the ice, it would seem as if the three little soft-furred, brown chaps that I had just driven from their snug wigwam had a far greater problem to solve than that of warmth or locomotion. How were they to breathe in the water beneath this foot-thick coating where was no hole to give them an outlet to the air? In a few minutes their lungs must have a new supply of oxygen, and if let alone they are able to get it in a rather curious fashion. Coming up beneath the ice, they expel the vitiated air, making a bubble which in a short time absorbs new oxygen from the ice and water; then they re-breathe it and go on.

In the early autumn when the ice is thin and clear you may capture Mussascus by first driving him from his lodge, then following him as he swims, a silvery streak beneath the ice, till he makes that telltale bubble. Then go up and hit the ice sharply over the bubble and you drive the little fellow away from his own breath and drown him. Put you would be unable to play any such mean trick as this along the Ponkapoag bog edge now, for the muskrats are abundantly provided for, and I believe they did it themselves.

Here and there along by their tepees you find open breathing holes. These, I am quite sure, the little fellows keep open, just to be able now and then to take a glimpse at the upper world, though they do not need them otherwise. But that is not the provision which I mean. As far along the bog front as the tepees go there are everywhere big white air-bubbles. From the tepees out into the pond they show in many places for a distance of a hundred feet, or more, and then cease. Nowhere else in the pond are these bubbles and I believe the muskrats have stored them here in their various excursions as relays, providing against just such folk as myself, who might come along, force them from their homes, and drown them beneath the thick ice covering. Thus provided, the three that I had driven out would have no trouble in reaching the most distant tepee or the higher bank beyond the bog edge, where are summer burrows.

Nor need they trouble their minds the winter through about provisions. Some curious skater or perhaps a would-be fur dealer has been along at one end of the bog and broken into a number of houses and scattered others all to bits. A long thaw enabled him to do this, else the winter had kept them so safe from vandals that only a heavy ax or pick would give entrance. Among the ruins that this human earthquake caused are fat roots of the yellow pond lily, the spatter dock, as long as my arm. It looks as if some of the houses were half built of these petrified reptiles broken in chunks, scaly looking remnants of a previous geological age. These are the, muskrat's bread, or perhaps we might better say his potatoes. Rough and forbidding as they look they are white and crisp inside, and though their taste is as flat and insipid as that of a raw potato to you and me the muskrat votes them delicious and satisfying. The bottom of the pond is stored with them and he has but to dive and dig, and he even buttresses his winter wigwams with them.

If he wants something a little more spicy there are spots in the bog, now safe under water and ice but within easy reach of a submarine like himself, where grow the pungent roots of the calamus, the sweet flag, of which he is very fond and which, when dried and sugared, most humans like to nibble. Stored all along the shallows are his shell-fish, the fresh water mussels whose thin shells he can easily tear open and whose white flesh he finds exceedingly toothsome. These, too, available in winter as in summer. Indeed some of his houses are built in the autumn, not so much for winter homes as restaurants where he may dine in seclusion on these very mollusks. Quite a distance from the bog, over in a shallow part of the pond, is a bed of these mussels with a flat-topped rock near by rising above the surface. Here last fall the muskrats built a lodge, right on the rock, which they used for this purpose. The first skaters kicked this lodge to pieces. It was fairly crammed with the empty shells of many a rare feast, showing that here Mussascus had undoubtedly entertained his friends in true Bohemian style.

So, while I shivered in the searching east wind on the sky side of the ice, the muskrats were well fed and comfortable in a region of even higher temperature, a country where the spring, which we say comes up out of the south, but the muskrat knows wells up out of the ground beneath, is already at his door. Its warmth is in the bog below and has softened and even melted the ice all about the tepees. The ice on the pond is a foot thick still, but the water beneath it is thrilled with this same potency and you have but to stir it to sniff its fragrance. Below the pond the brook which is its outlet splashes over the long-abandoned sills of what was a gristmill dam in the days of the early settlers. Here in spite of the keen lances of the wind and its roar in the frozen maples overhead, I heard the soft tones of the coming season in every babble of the brook. All the air was full of a fresh, inviting fragrance which the water gives off as it flows. All the pond is full of it beneath the ice already, and the muskrat breathes it in his every excursion under the crystal depths. Soon he will abandon the winter houses, which as soon as the frost leaves  them will sag and flatten and begin to sink into the bog itself, building its outer edge a little firmer here and there, and thus helping it in its yearly encroachment on the pond itself. As the ages have gone by, Mussascus has been a pretty potent factor in this encroachment.

As the beaver has been a maker of ponds and a conserver of streams, holding and delaying their waters with his dams, so the muskrat has helped in the making of meadows and the sanding and grading of pond edges. The first is done by his winter nests, the second by his summer burrows which start under water at the pond edge and slant along near the surface for thirty to fifty feet. Many cubic yards of sand and loam are dug from these burrows and spread along in the shallows. His river habits are strong upon him in this work, for he usually makes a delta of entrances, three or four leading up into the same passage which often has a wee exit above water, near the edge. Here if you are particularly fortunate you may in midsummer see his young poke their noses up; longing for a peek at the great world, before they are big enough to swim out into it. Here, too, weasel and mink sometimes find entrance and devour his family. But there are three litters a year, as a rule, so the occasional weasel serves to keep down a too great increase in the population.

His greatest enemy, however, is man, who so pollutes the streams with sewage factory refuse that no self-respecting muskrat can live in many of them, and who hunts him for his fur for the making of automobile coats, yet in the case of my Ponkapoag Pond friends man's hand for once is for him rather than against. His home there is now a part of the park system and he may be shot or trapped only under penalty of the law. This has been so for some years now and I think it explains the numbers of the winter lodges which are this year greater than ever before.