Walking the other day in an old hemlock wood, I counted over forty varieties of these summer visitants, many of the common to other woods in the vicinity, but quite a number peculiar to these ancient solitudes, and not a few that are rare in any locality. It is quite unusual to find so large a number abiding in one forest,--and that not a large one,--most of them nesting and spending the summer there. Many of those I observed commonly pass this season much farther north. But the geographical distribution of birds is rather a climatical one. The same temperature, though under different parallels, usually attracts the same birds; difference in altitude being equivalent to the difference in latitude. A given height above sea-level under the parallel of thirty degrees may have the same climate as places under that of thirty-five degrees, and similar flora and fauna. At the head- waters of the Delaware, where I write, the latitude is that of Boston, but the region has a much greater elevation, and hence a climate that compares better with the northern part of the State and of New England. Half a day's drive to the southeast brings me down into quite a different temperature, with an older geological formation, different forest timber, and different birds,--even with different mammals. Neither the little gray rabbit nor the little gray fox is found in my locality, but the great northern hare and the red fox are. In the last century, a colony of beavers dwelt here, though the oldest inhabitant cannot now point to even the traditional site of their dams. The ancient hemlocks, whither I propose to take the reader, are rich in many things besides birds. Indeed, their wealth in this respect is owing mainly, no doubt, to their rank vegetable growth, their fruitful swamps, and their dark, sheltered retreats.