Page:The American Cyclopædia (1879) Volume X.djvu/465

 LIGHTHOUSE 459 were not intended for occupation by the keep- ers. There are four stories, all of different orders of architecture, and adorned with busts and statues of kings of France and heathen gods. The material is stone. The basement or lower story appears to have been intended as a store room ; the second story is called the king's apartments ; the third is a chapel, and the fourth consists of a dome supported by columns, a kind of lower lantern ; above this was originally a lantern formed of a stone dome and eight columns. The total height of the tower from its base to the upper point of the lantern dome was 146 ft., and from the rock 162 ft. In the upper lantern a fire of oak wood was kept burning at night for about 100 years, when, in 1717, the fire having weak- ened the stone supports by calcining them, the upper lantern was taken down and the light was kept up in the lower lantern. As it did not show well there, an iron lantern was erect- ed in 1727 above this, in the place of the old stone lantern, and coal was used for fuel in- stead of wood. It is worthy of remark that the upper part of this lantern contained an in- verted cone, the base of which was the base of the lantern dome. The surface of the cone was covered with tin plates, thus forming a rude reflector that utilized a part of the light, which without it would have been lost. This was probably the first attempt made in a light- house to deviate the rays of light so as to throw to the horizon those which would have been lost in the upper parts of the atmosphere. The Cordouan lighthouse is also notable from the fact that the first Fresnel lens manufactured was placed in it in 1823. The Eddystone light- house (see EDDYSTONE ROCKS) is celebrated on account of the difficulties attending its construc- tion, and the fact that it is the type of all struc- tures of the kind which have since been erected. The Eddystone rocks in the English channel, near the port of Plymouth, are in the fairway of all vessels coasting along the S. shore of England, and the attention of the government was directed to them at an early day. They are a cluster of gneiss rocks 600 or 700 ft. long from N. to S., with detached rocks covering about the same distance from E. to W. The highest part of the rock upon which the light- house is placed is about 16 ft. out of water at low water of spring tides-. The first lighthouse erected upon them was commenced in 1696 and finished in 1699 by Henry Winstanley. The accounts of its construction are vague, but it is supposed to have had a solid circular and polygonal stone base 12 ft. high and 24 ft. in diameter, upon which was built a structure of wood resembling a pagoda. The height from the rock to the base of the lantern was about 75 ft. The lantern was glazed. This building stood until November, 1703, when Mr. Win- stanley went to the lighthouse with a party of workmen to make some repairs. On the 26th of the month a terrible storm arose, and not a remnant of the lighthouse nor a trace of its inmates was ever seen afterward. The fact that a lighthouse could be made to stand on the Eddystone having been demonstrated, soon after the destruction of Winstanley's building another was built by Rudyerd. It was com- menced in 1706 and finished in 1709. It was an ingenious combination of wood and iron, and showed great advances in the art of engi- neering. The form was the frustum of a circu- lar cone. It was built up nearly solid for a height of 27 ft. above the rock, the filling consisting of courses of cut stone alternating with courses of squared timber. The outside casing was composed of 72 oak posts or up- rights, the lower ends of which were fastened to the rock by heavy irons which were let into lewis holes. This is the first recorded applica- tion of the lewis for this use. The lantern was glazed. This building stood well with some repairs of the woodwork until December, 1755, when it was de- stroyed by fire. The fire commenced in the lantern in the early part of the night, and the keep- ers retreated from room to room until they reached the rock. Early in the morning they were brought to the shore, as the weather hap- pened to be good enough to permit a boat to land on the rock. In 1756 Smea- ton was selected to rebuild the Eddy- stone. He deter- mined to use stone for the material, and the shape of the trunk of a large tree as his model. The stones of a course were joined by dove- tailing, and the different courses were con- nected by stone dowels. The upper surface of the rock was cut in horizontal steps, so that every course of masonry rests upon a horizontal bed. The general form of Smea- ton's structure is the frustum of a cone, or more strictly that of a solid of revolution formed by revolving a vertical plane bounded on one side by a concave curve around a verti- cal axis. The elevation, or a vertical section of the tower, indicates great strength. The diam- eter of the lowest partial course is 32 ft., and that of the first or lowest entire course is 26 ft. The diameter of the course under the coping is 15 ft., and the whole height of the masonry is 77 ft. The tower is surmounted by a parapet wall 6| ft. high and 8f ft. in internal diameter. The combinations devised for obtaining the greatest strength in this tower by dovetail- FIG. 8. Eddystone Lighthouse.