Some years later, a beaver house, the side of which had been cut away, afforded an opportunity for us to learn how our white-headed friend finished the inside of his castle. The rough projecting inner ends of sticks, branches and brush were gnawed off making a roomy, smooth-walled, dome ceilinged space divided into two parts. The first, or ground floor, contained the openings for entrance and exit. It also was used as a drying room; for no self-respecting beaver would ever permit himself, his family or guests to go to bed in wet clothes. Coming in from swimming in the pond or river he must sit in the vestibule until his wet fur is thoroughly dry before he climbs into the bunk.
The drying floor also serves the purpose of a dining room in winter, when the pond is covered with ice, as will later appear.
The sleeping apartment had its floor about six inches higher than the drying floor. The bed was made of thin shreds or splinters of dry poplar wood. A quantity of this material had been split out with an expenditure of much time and patience. A mattress three inches or more thick, made of this soft, elastic material would make a far better bed than many campers can boast of.
Mud for use in house building was procured, not only from the tunnel entrances and from the canal, but excavations were made in the river bottom near the house. A pocket was there dug out, about twenty feet in diameter, making the water six feet deep.
Into this hole the two beavers now proceeded to store their food for the winter. This consisted chiefly of the trunks of poplar saplings, two to six inches in diameter, cut into lengths of four to six feet, the sticks of larger diameter being the shorter. In the wood pile were also placed the branches of the same trees. Mixed in with the poplar were some alders and a few birch and soft maple sticks. The birch and alder apparently were used to add spice and tang to the otherwise sameness of their more staple food.
In the edge of the forest next the slough a few years before, a fire (doubtless started by some careless hunter), had burned over several acres, and this was now covered by a "second growth" of poplar. It was there that the beavers cut most of their lumber. The water in the slough was shallow and filled with pond lilies, so a canal three feet wide, two feet deep and two hundred and twenty feet long was dug across this mudhole. Through this canal the beavers floated their sticks and brush and placed them on their storage pile under water so that the bark, which they eat, might be kept soft and fresh for winter use. Also, so that it might be reached from their house under the ice, after pond and river were frozen.
Day after day Bige and I watched the progress of this harvest. Saw the beaver towing the floating logs through the canal into the pond and up the river to the lumber pile where the beaver would dive with his stick and presently come to the surface again, leaving the stick under the water; and we wondered how he did it. Also we discussed possible ways of making a floating stick sink. From our boat we could see the pile of wood below the surface of the water and we could see no stones on the pile.
Bige stoutly argued in support of the theory that the beaver sucked the air out of the pores in the wood, that the water flowed into the vacuum thus produced, making the stick heavy enough to sink. In order to demonstrate his theory, Bige took the axe from camp, cut a poplar sapling an inch and a half in diameter and the usual beaver length, put one end in the water and sucked on the other end of the stick. After repeated trials and failures to make the stick do anything but float, Bige decided that his "sucker was not powerful enough." The next day, looking down into the water from our boat, we saw one end of the axe-cut stick in the wood pile with other sticks cut by beaver teeth.