TECHNICAL REFERENCES TO THE PLATES.
" Plate plan and perspective elevation if the Eddystone Rock, as seen front the west ; showing also the theodolite.
" The representation is as I found the rock ; Figure 1 being the plan, and Figure 2 the upright view. 'rile settle letters refer to the same parts in both; the cross lines upon the plan answer to the cardinal points, east, west, north, and south, according to the true meridian.
" L is the landing-place, and e the summit of the rock ; the general declivity being towards the south-west ; the grain of the laminated moor-stone that composes it being nearly parallel thereto. It has, however, considerable irregularities; for upon the line A B the rock makes a sudden drop of four and a half or five fret ; and, by overhanging to the westward, when there is a ground-swell at south-west, the sudden check causes the sea to fly in an astonishing manner, even in moderate weather.
"The surface of the rock is shown, as supposed to have been for ages past ; except where it is visibly altered by mart's hand, chiefly within the circular area of the late build ing. The flat treads of the steps cut by fludyerd are marked n ; the upright fitees of the steps F ; and E denotes the spawled parts, parallel to the grain of the rock.
"abcdefyli show the remains of the cavities of eight of the twelve great irons fixed by Winstanley ; of which the stump of one only, viz., that at c, remained for my inspection ; it was run in with lead, and had continued fast, till in planting a dovetail there it was cut out, and found club ended. Which of the other holes, that are left unmarked, made up the remaining four, I could not make out ; as doubtless several of them appertained to the additional work that he fixed in the fourth year.
"'Figure 3. A pair of 1Zudyerd's iron branches, to a scale three times larger than that of the plan ; wherein A n is the main branch, or dovetail part ; c n the key, driven hard in, but touching the bottom ; their depth in the rock is denoted by supposing the line 13 e its surfitee. The holes in
the branches served to fasten the timbers. by large bearded spike-bolts. Of those branches I traced thirty-six original pairs, of dif•rent sizes; and two more modern : their places are shown in the upright, Figure 2, by inspection ; and like wise in the plan, Figure 1, at 1, 2, 3, 4, 5, and 6, 7,8, 9, 10, &c. forming a double circle ; also two pair of them at K, to fix the mast, on two sides, to the centre. The irons that remained in the rock, are distinguished in the plan by being hatched with slant lines, the empty holes or cavities by being black. Those that remained whole, whether fast or loose, are dis tinguished in Figure by their shapes.
"x. The place of the cave on the cast side.
" R. A strong ring-bolt, put into the rock on the recom mencement of the building in 1757, for fastening the western guy-chain of the shears.
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" Figure 2, rstv 2c. The three-legged stool, steadied with cross-braces. Upon the middle of the upper round plank r s was screwed down the theodolite T, to whose index was screwed the long horizontal rule v s, divided into feet, inches, and parts, upon one edge, tending to the centre. Upon any marked point of the rock to be ascertained, sup pose .r, the rod x y was set upright by a spirit-level, and was preserved in an upright position by two small slips of deal, applied as shores or struts, in two different directions. The divided edge of the rule being brought against the upright rod, was shoved up by a short staff, held in the hand tight against the rod, till a spirit-level laid upon the top of the rule showed it to be level. In this position the index would show the degree and minute of the circle ; the upright rod would mark the distance from the centre upon the rule; and the rule would mark open the rod, how much the intersection was above its bottom at x.
" Rate II. No 1.—South elevation of the stone lighthouse completed upon the Eddystone in 1159.