As a general rule, the buoys in a river channel are painted red, striped with white, if the homeward-bound vessel is to leave them on the right; and black, when she has to pass them on the left. Others are painted with horizontal stripes of red and black, or in squares and diamonds, according to the various purposes they are intended to serve. Obstacles, such as wrecks, are marked by green buoys. A buoy, recently invented by Mr. Hubert, and adopted by the Trinity Board, is so constructed, with regard to the centre of flotation, and the point where the mooring-chain is attached, that it will keep upright in almost any weather. Another buoy, invented by Messrs. Brown and Lenox, is ingeniously contrived to render its _bell_ audible even when the buoy itself is not visible; the stream of water passing through the lower part of the framework keeps in motion an undershot water-wheel, which incessantly rings the bell. The average size of the buoys now in use is about eight feet, but many are of larger dimensions; and some, like North-east Spit Buoy, at the east end of Margate Sand, are twenty feet. Various plans for lighting them have been suggested, but with no very successful result. The only felicitous instance is that of the Arnish Beacon on the north coast of Scotland; it consists of a cone of cast-iron plates, surmounted with a lantern containing a glass prism. The prism is illuminated by a light directed upon it from Stornaway Lighthouse; and so perfect is the deception that the fishermen long refused to believe there was not a real light on the beacon. [Illustration: THE ARNISH BEACON.] Nearly a thousand buoys are posted about the coast of England and in the channels of her principal rivers. Scotland and Ireland have about two hundred each. These bear their own particular denominations, forming a very diversified and somewhat amusing vocabulary. We find amongst them an “Eagle,” a “Gull,” a “Swallow,” a “Horse,” a “Mussel,” a “Firefly;” also a “Cutler,” a “Constable,” a “Columbine,” and a “Fairy;” a “Royal Sovereign,” a “Protector;” and a “Tongue,” an “Elbow,” and a “Longnose.” The position of every buoy on the British coast is verified once a quarter; and every half-year—that is, in March and September—all buoys, except the largest, are “shifted,” being replaced by clean ones. After a certain period of immersion they lose their brilliancy of colour, and become encrusted with salt, as well as with organic matter. “Buoy-shifting,” says a recent writer, “is a duty which calls forth all the skill and energy of the officers and men comprising the crews of the Trinity House vessels, for the buoys are mostly placed to indicate the position of dangerous shoals, and not unfrequently the change is effected under very inauspicious circumstances. The buoys brought in are carefully examined, and if fit for further use, repainted and repaired.” The cost of a buoy varies, according to its size, from twenty-five to two hundred and fifty pounds.