One gray day while I was examining a beaver colony there came another demonstration of the usefulness of beaver ponds. The easy rain of two days ended in a heavy downpour--a deluge upon the mountainside a mile or so upstream. There was almost nothing on this mountain either to absorb or delay the excess of water which was speedily shed into the stream below. Flooding down the stream's channel above the beaver pond, came a roaring avalanche of water, or water-slide, with a rubbish-filled front that was five or six feet high. This expanded as it rolled into the pond, and swept far out on the sides, while the water-front, greatly lowered, rushed over the dam. A half a dozen ponds immediately below sufficed so to check the speed of this water and so greatly to reduce its volume that as it poured over the last dam of this colony it was no longer a flood. The regulation of stream-flow is important. There are only a few rainy days each year, and all the water that flows to the sea through river-channels falls during these few rainy days. The instant the water reaches the earth it is hurried away by gravity, and unless there are factors to delay this run-off, the rivers would naturally contain water only on the rainy days and for a little while thereafter. A beaver dam and pond together form a factor of importance in the keeping of streams ever flowing. The pond is a reservoir which catches and retains some of the water coming into it during rainy days and which delays the water-flow through it. A beaver pond is a leaky reservoir, a kind of spring as it were, and if stored full during rainy days the leakage from it will help maintain stream-flow below during the dry weather. Beaver works thus tend to distribute to streams a moderate quantity of water each day. In other words they spread out or distribute the water of the few rainy days through all the days of the year. A river which flows steadily throughout the year is of inestimable value to mankind. If floods sweep a river, they do damage. If low water comes, the wheels of steamers and of factories cease to move, and a dry river-channel means both damage and death. Numerous beaver colonies along the sources of countless streams that rise in the hills and the mountains would be helpful in equalizing the flow of these streams. I hope and believe that before many years every rushing care-free brook that springs from a great watershed will be steadied in a poetic pond that is made, and that will be maintained by our patient, persevering friend the beaver.