Nothing can be more striking to one who is accustomed to the little inclosures called public parks in our American cities, than the spacious, open grounds of London. I doubt, in fact, whether any person fully comprehends their extent, from any of the ordinary descriptions of them, until he has seen them or tried to walk over them. You begin at the east end of St. James's Park, and proceed along its graveled walks, and its colonnades of old trees, among its thickets of ornamental shrubs carefully inclosed, its grass-plots maintained in perpetual freshness and verdure by the moist climate and the ever-dropping skies, its artificial sheets of water covered with aquatic birds of the most beautiful species, until you begin almost to wonder whether the park has a western extremity. You reach it at last, and proceed between the green fields of Constitution Hill, when you find yourself at the corner of Hyde Park, a much more spacious pleasure-ground. You proceed westward in Hyde Park until you are weary, when you find yourself on the verge of Kensington Gardens, a vast extent of ancient woods and intervening lawns, to which the eye sees no limit, and in whose walks it seems as if the whole population of London might lose itself. North of Hyde Park, after passing a few streets, you reach the great square of Regent's Park, where, as you stand at one boundary the other is almost undistinguishable in the dull London atmosphere. North of this park rises Primrose Hill, a bare, grassy eminence, which I hear has been purchased for a public ground and will be planted with trees. All round these immense inclosures, presses the densest population of the civilized world. Within, such is their extent, is a fresh and pure atmosphere, and the odors of plants and flowers, and the twittering of innumerable birds more musical than those of our own woods, which build and rear their young here, and the hum of insects in the sunshine. Without are close and crowded streets, swarming with foot-passengers, and choked with drays and carriages. These parks have been called the lungs of London, and so important are they regarded to the public health and the happiness of the people, that I believe a proposal to dispense with some part of their extent, and cover it with streets and houses, would be regarded in much the same manner as a proposal to hang every tenth man in London. They will probably remain public grounds as long as London has an existence.