While watching the autumnal activities of this colony, as described in another chapter, I broke through the surface and plunged my leg into an underground channel or subway that was half filled with water. Taking pains to trace this stream downward, I found that it emptied into the uppermost of the ponds along with the waters from a small spring. Then, tracing the channel upwards, I found that, about one hundred and forty feet distant from the uppermost pond, it connected with the waters of the brook on which the old colony formerly had a place. This tunnel over most of its course was about two feet beneath the surface, was fourteen inches in diameter, and ran beneath the roots of spruce trees. The water which the tunnel led from the brook plainly was being used to increase the supply needed in the canals, ponds, and pools of the Spruce Tree Colony. The intake of this was in a tiny pond which the beaver had formed by a damlet across the brook. That this increased supply of water was of great advantage to the busy and populous Spruce Tree Colony, there can be no doubt. Was this tunnel planned and made for this especial purpose, or was the increased water-supply of the colony the result of accident by the brook's breaking into this subway tunnel? The canals which beaver dig, the slides which they use, the trails which they clear and establish, conclusively show that these animals appreciate the importance of good waterways and good roads,--in other words, good transportation facilities. The Primitive House The Lily Lake beaver house, in which the old beaver spent the drouthy winter, was a large roughly rounded affair that measured twenty-two feet in diameter. It rose only four feet above the normal water-line. This house had been three times altered and enlarged, and once raised in height. Its mud walls were heavily reinforced with polelike sticks, which were placed at the junctures of the enlargements. The one large room was more than twelve feet in diameter. Near the centre stood a support for the upper part of the house. This support was about one and a half by two and a half feet, and was composed for the most part of sticks. But few houses have this support; commonly the room is vaulted. The room itself averaged two and a half feet high. It had four entrances. A house commonly has two entrances, but it may have only one or as many as five. Thus the way to the outer world from the inside of the house is through one or more inclined passageways or tunnels. The upper opening of these entrances is in the floor a few inches above the water-level, and the lower opening in the bottom of the pond under about three feet of water. These extend at an angle through the solid foundation of the house, are about one foot in diameter and four to fifteen feet long, and are full of water almost to floor-level. This dark, windowless hut has no other entrance.