The British firm has established a unique reputation, as it has been responsible for the majority of the great lights of the world, some of which are not only of huge dimensions and weight, but also of novel form. The hyperradial apparatuses which have been placed recently in the towers of Manora Point and Cape Race probably rank as the most powerful and the finest in existence. These are used in conjunction with the petroleum vapour incandescent burner. The Cape Race light, for instance, comprises a revolving optic of four panels, subtending a horizontal angle of 90 degrees, with a vertical angle of 121½ degrees. Each lens comprises the central disc, or bull’s-eye, around which are placed nine rings of glass, giving a total refracting angle of 57 degrees. In order to bend the vertical rays into a horizontal path twenty-two catadioptric reflecting prisms are disposed above the lens, while below are thirteen similar prisms. The total amount of glass worked into the four panels is about 6,720 pounds, and the prisms are mounted in gun-metal frames, which weigh approximately 4,800 pounds, so that the total weight of the glass portion and its mounting alone, standing some 12 feet in height, is over 11,500 pounds. The installation completed for the equipment of the Manora Point lighthouse, Karachi, is very similar. In some cases the demand for a powerful light has been met with a system differing from the “hyperradiant.” The lenses and respective groups of refractors are superimposed, each tier having its individual burner and flues for carrying off the products of combustion. In this way we have the biform, comprising two such panels arranged one above the other, as in the Fastnet and Eddystone lights; and the quadriform, wherein four tiers are built one above the other, as installed at the Mew Island light in Ireland. The advantage of this arrangement is that a beam of great intensity is secured with a lantern of comparatively small diameter. The French authorities adopted a modification of this system. Instead of placing two lenses and refractors one above the other, they ranged them side by side, the effect being analogous to a couple of squinting eyes, the panels being parallel and therefore throwing out parallel beams. But these adaptations have not come into extensive use, as they have been superseded by more simple means of achieving similar requirements with an even more powerful ray. The hyperradiant stands as the finest type of apparatus yet devised, and therefore is employed when an extremely powerful light is required. While the design and arrangement of the optical apparatus is certainly a most vital and delicate task, the mounting thereof upon a substantial support in such a way that it may perform its work with the highest efficiency is equally imperative, since the finest apparatus might be very adversely affected by being improperly mounted. [Illustration: FIG. 12.--APPARATUS SHOWING A DOUBLE FLASH, FOLLOWED BY A SINGLE FLASH.