In order to obtain a firm foundation, he divided the surface of the rock into seven slightly unequal stages, and in these he dug or excavated six and thirty holes, varying in depth from twenty to thirty inches. Each hole was six inches square at the top, gradually narrowing to five inches, and then again expanding and flattening to nine inches by three at the bottom. Into these dove-tailed cavities or sockets were inserted strong iron bolts, weighing from two to five hundredweight, according to length and structure. These bolts held fast a course of squared oak-timbers laid lengthwise on the lowest of the seven stages, so as to reach the level of the stage or step immediately above it. Another set of beams was then laid diagonally covering those already laid, and raising the level surface to the height of the third stage. The next course was deposited longitudinally, and the fourth diagonally, and so on alternately, until a basement of solid timber was erected, two courses higher than the highest point of the rock. [Sidenote: His lighthouse.] Rudyerd's lighthouse is generally described as a fabric of wood; but this is incorrect. To obtain the necessary solidity, and a sufficient weight to counteract the weight of the waters of the Channel, he combined courses of Cornish granite with his courses of timber, in the proportion of five to two, so far as the basement went: that is, he laid two courses of timber, and then five of granite, and then two more of timber; all being firmly secured by iron bolts and cramps. On this substructure, which measured 63 feet in height, with a base of 23 feet, he raised four stories of timber, crowned by an octagonal lantern, 10 feet 6 inches in diameter, and a ball of 2 feet 3 inches in diameter. The total elevation, from the lowest surface of the rock to the top of this ball, was 92 feet. Rudyerd completed his work in 1709. [Sidenote: On fire!] For a long period of years, nearly half a century, it withstood the attacks of wind and wave, and many a vessel was kept from destruction by its warning light. On the 2nd of December 1755, it was fated to fall before an unexpected enemy. There were three keepers resident in the lighthouse at the time. One of them, whose turn it was to watch, entered the lantern, at about two o'clock A.M., to snuff the candles, and, to his horror, discovered it to be filled with smoke. On opening the door which led to the balcony, to permit of its escape, a flame instantly leaped from the interior of the cupola. He hastened to alarm his companions, and vigorous efforts were made to extinguish the fire; but these proved ineffectual, owing to the dryness of the woodwork, and the difficulty of raising a sufficient supply of water to the top of the building. Fortunately for the keepers, the flames were descried from the shore, and a well-manned boat put off to their relief.