Some lights are of the flashing type, and in this instance the reflectors are disposed in groups. Here the gimbals, carrying the reflectors, are mounted upon the framework which revolves around the mast by clockwork mechanism, and are so arranged as to give any type of distinguishing flash that may be desired. In the most approved types of modern lightships, however, the dioptric apparatus is incorporated, means having been discovered to avoid breakage from the rolling motion of the ship, while the risk of throwing the beam above or below the horizon according to the rolling of the boat is overcome. In this case the lamps and reflectors are disposed on a turntable in the lantern, with the dioptric apparatus mounted very carefully so as to secure a true balance upon gimbals. The apparatus for revolving the light is erected in a deck-house, the weight actuating the mechanism being permitted to rise and fall in a special tube extending from the bottom of the ship to the deck. The rotary action thus produced is transmitted from the deck to the lantern above by means of a vertical shaft and pinion. While ordinary lamps are installed as a rule in the lanterns, Messrs. Chance Brothers and Co., the Birmingham lighthouse illuminating engineers, have succeeded in adapting their incandescent oil-vapour system, which has proved so eminently successful in lighthouses, to light-vessels, with a very decided increase in the candle-power, and marked economy in oil consumption and cost of upkeep. CHAPTER XX A FLAMING SENTINEL OF THE MALACCA STRAITS With the development of commerce between Europe, China, and Japan, following the awakening of the East, it became imperative to render the seas approaching these countries far safer to navigation. If one consults the atlas, and follows the routes taken by the great liners from Britain and the Continent to the Orient, he will see a rampart forming the boundary between the Indian Ocean and the South China Sea. This is the East Indian Archipelago, and it bristles with dangers of all descriptions to the mercantile traffic flowing to and fro. After leaving India, the steamships turn their noses towards Singapore, at the extremity of the Malay Peninsula; but this busy port is shut in on the south by the attenuated rocky chain of islands forming the Dutch East Indies, of which Sumatra and Java are the most important. The steamship lane lies between Sumatra and the Asian mainland, and is known as the Straits of Malacca. It is a fearsome neck of water, studded with islands and sandbanks, some visible above high-water, others revealed only by the falling tide; while still more never see daylight at all, yet owing to their shallow position are none the less perilous.