There are also sheets of water in Regent's Park, Victoria Park, Battersea Park, St. James' Park, and Kensington Gardens. The sheet of water, or stream, in Hyde Park, is known as the "Serpentine River," from its sinuous course. This is quite a large sheet of water, and is much frequented for free bathing, on warm days in the heated term. Here, thousands of people may be seen on a sultry afternoon, plunging to and fro in the cool waters, and in case of any accident--for the water is deep--the boats, ropes and drags of the Royal Humane Society's Life Saving Apparatus, are always ready for immediate use, and numbers of people are rescued and taken from the Serpentine, and resuscitated. When the winter months come, and the Serpentine becomes frozen over, the Londoners congregate there in great numbers to skate, or play at golf or curling. There is a large lake in the Regent's Park ornamented with small, well-wooded islands, and in Kensington Gardens there is one of the finest museums of art, science, and curiosities, in the world. There are rocky dells, and grounds for sham fights, in Hyde Park, there are the rarest exotics in the Palm House at Kew, and every known species of bird, beast, reptile, and fowl, may be found in the Zoological Gardens, which comprises eighteen acres of space in the Regent's Park. In Richmond Park, which is ten miles distant from the London Post Office Centre, there are two thousand three hundred acres of hill, dale, plain, and forest, and here are to be found deer-parks, rabbit warrens, romantic foot-paths, ancient oaks, horse-chestnuts, and thorny ridges, with a variety of sequestered spots for pic-nics and pleasure parties. This noble park can be reached by a sail of fifteen miles on the River Thames, which is skirted by Richmond Park for some distance. There is a grand Observatory for scientific purposes in Greenwich Park, which is noted all the world over for its correct calculations, and all the watches and clocks in Great Britain are set by Greenwich time. [Sidenote: THE WORLD'S FAIR.]