The holes made to receive the iron branches, appear to have been drilled into the rock by jumpers, making holes of about 21 inches diameter; the extremities of the two holes forming the breadth for the branch, at the surface of the rock, were about 7+ inches ; and these holes were directed so that at their bottoms they should be separated somewhat better than an inch more, that is, so as to be full SI inches. In the intermediate space, a third hole was bored between the two former ; and then it' the three holes were broken into one, by square-faced pummels, this would make, the holes sufEeiently smooth and regular. By this means he obtained holes of a dove-tail shape, being 2I inches wide, 7} broad at top, Si at bottom, and 15 and 16 inches deep; and as these could not be made all alike, every branch was forged to lit its respective hole. The main pieces of each branch, were about 41 inches broad at the surface of the rock, and 6} at the bottom; and this being first put down into the hole, the space left for a key would be 3 inches at top, and 2 inches at bottom, which would admit it to be driven in so as to render the whole firm, and the main branch fixed like a dove-tail or Lewis.
• The holes being each finished, and fitted with their respective branches, and cleared of water, a considerable quantity of melted tallow was poured into each hole : the branch and key being then heated to about a blue heat, and pm down into the tallow, and the key firmly driven, all the space unfilled by the iron, would become full of tallow, and the overplus made to run over : when this was dune, all remaining hot, a quantity of coarse pewter, being made red hot in a ladle, and run into the chinks, as being the heaviest body, would drive out the superfluous melted tallow : and so effectually had this operation that in those branches which were cut out in 1756, and had remained tlist, the whole cavity had continued so thoroughly full, that not only the pewter, but even, in general, the tallow, remained apparently fresh : and when the pewter was melted from the irons, the scale appeared upon the iron, as if it had come from the smith's forge, without the least rust upon it.
" All the iron branches, which are shown, as I found them, in Plate 1, having been fixed in the manner above mentioned, they next proceeded to lay a course of squared oak balks, lengthwise upon the lowest step, and of a size to reach up to the level of the step above. Then a set of short balks were laid crosswise of the former, and upon the next step compoundedly, so as to make good up to the surface of the third step. The third stratum was therefore again laid lengthwise, and the fourth crosswise, Ste., till a basement of solid wood was raised, two complete courses higher than the highest part of the rock ; the whole being fitted together, and to the rock, as close as possible, and the balks, in all their intersections with each other, trenailed together. They were also fitted to the iron branches where they happened to fall in ; for the branches do not seem to have been placed with any complete regularity or order, but rather where the strength and firmness of the rock pointed out the properest places for fixing them; they were, however, to appearance disposed so as to form a double circle, one about a foot within the circumference of the basement, and the other about three feet within the former ; besides which, there were two large brandies fixed near the centre, for taking hold of the two sides of a large upright piece of timber, which was called the mast ; by which two branches it was strongly fixed down ; and being set perpendicular, it served as a centre for guiding all the rest of the succeeding work.
"The branches were perforated, in their respective upper parts, some with three, and some with four holes ; so that, in every pair (collectively called a branch) there would beat a medium seven holes ; and as there were at least thirty-six original branches, there would be 252 holes, which were about seven-eighths of an inch in diameter ; and, conse quently, k capable of receiving as many large-bearded spikes, or jag-bolts, which being driven through the branches into the solid timber, would undoubtedly hold the whole mass firmly down ; and the great multiplicity of trenails in the intersections, would confine all the strata closely and compactly together.
" I cannot omit here to remark, that though the instrument we now call the lewis, is of an old date, yet, so tar as appears, this particular application of that idea, which Mr. Rudyerd employed in fixing his iron branches firmly to the rock, was made use of for the first time in this work : for though Mr. \Vinstanley mentions his having made twelve holes, and fixed twelve great irons in the rock, in his first year's work, yet he gives no intimation of any particular mode of fixing them, but the common way with lead ; and the stump of one of the great irons of Mr. Winstanley's, that was cut out in the course of the work of the summer of 1756, was fixed in that manner ; but we remarked, that the low end of this bar or stanchion, was a little club-ended, and that the hole was somewhat under-cut ; so that, when the lead was poured in, the whole together would make a sort of dovetail engraft tnent : however, when these irons, by great agitations, became loose, and the lead yielded in a certain degree, they would be liable to be drawn out ; as the orifice by which they entered must have been large enough to receive the iron club. Mr. Iludyerd's method, therefore, of keying and securing. must be considered as a material accession to the practical part of engineery ; as it furnishes a secure method of fixing ring-bolts and eyebolts, stanchions, &c., not only into lucks of any known hardness ; but into piers, moles, &e., that have already been constructed, for the safe mooring of ships ; or fixing additional works, whether of stone or wood.