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. But 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 their summer burrows.