While the stone is hoisting, the man represented at r is heaving,-in the tackle-fall of the runner and tackle it n: for, till the stones arc cleared of the boat, the shears lay out con siderably, and the out-hawler guy-rope, L NI, is slack. This crosses the gut, and is fixed by a ring-bolt to one of the rocks of the south reef liv such time, therefore. as the stone is hoisted by the main tackle to the height of the entry-door, the shears are got into the perpendicular; and then by easing the out-bawler guy-tackle, L IC, the stone comes into the entry door.
The runner and tackle n l? is hooked to the guy-chain, 0, which crosses the work, and passes down to the ring On the west side of the rock ; marked n in Plate I.
"In the detached Figure 2, the anchor-like piece of iron, by which the main tackle-blocks are hung, is to an enlarged scale at e f g h. This anchor being suspended upon a round bolt at c, that passes through the tops of the two shear legs, swings freely between them, and always putting itself in a perpendicular position, and producing lair bearings upon them, without any unnatural strain or twist, enables them to support the greatest weight possible.
"In like manner the two arms of the- anchor g h, having the two guy-tackles hooked to them, the action of those tackles is upon the suspending bolt, and the feet of the tehears turning freely upon •ye-ImIts fixed in the rock, they are at liberty to conform themselves to the position wanted ; so that the stress upon the legs is always endwise.
"After the building was raise-el to the height shown Figure I, the work was hoisted through the well-hole, till it arrived at the top of the solid. by means of the triangle and twelve-fold blocks wherewith the work was set ; and are shown as standing upon the wall at the first vaulted floor by the letters i k 1 m, being the timrth stage: bat after that was completed (the limn-hole being too small, and the height ton great, without losing time) a jack-roll was established, as shown at the third stage in the lower store-room at 31: and a pair of movable shears, the figure w hereof is sl.own at the fifth stage, as upon the wall, at the kitchen-fluor ; which, instead of guy-ropes, had a back leg, longer than the rest, whose bottom or imit cut with a notch, stepped upon the internal angle of the opposite wall ; and was long enough to suffer them to lean over sufficiently fir the stone at p to clear the wall. The shears thein-wlyes were prevented from falling
over by a 1dr-tackle, shown upon the back leg, whose lower block hooked upon a lewis, in that stone the back leg stepped upon; by which it was brought tight and steady. When the stone was to be landed, this tackle 'being a little slacked, till the notch could be disezg»geI, and then set upon, the back leg would, by going over the wall, suffer the shears to conic to the perpendicular, or beyond it.
" The stones, now become in general less weighty, a com mon tackle was employed at the shear-head. which would go down to the entry door, and there mut the stones hoisted by the great shears: the tackle-fall of the movable shears, being taken to the jack-roll 2, the stones were got to the top of the building, in the same tulle they were raised from the boat to the entry-door.
The detached figure it is the plan of the movable shears ; \diem the check, or safety rope, n, is shown at the foot of the back leg.
In this manner all the heavy materials were got up; the movable shears rising with the work, till the cupola was to be set upon the lantern.
"The sixth stage shows the apparatus used for this pur pose. The great shears being now done with, were taken down and put through the windows of the uppermost room, and there, being well steadied, served as booms. The detached figure s being the plan of this stage, shows their particular disposition; wherein op show the places or feet of the legs of the shears used for this particular !impose; also marked with the same letters in the relative upright. In this, the rope q r shows it side-stay to the leg a r; s/ is the stay of the leg p 1, each fastened to q s, the extremes of the booms.
"From each end of the cross-tree at the head of the shea•-poles proceeded the ropes 10 .r, y x, which, joining in one goy-rope at X, proceeds over a pulley in the end of the temporary timber at z: from thence, with the intermediation of a tackle, 1, 2, it proceeds to, and fixes at the extreme end of the boom 3; and as the weight to be hoisted will prin cipally lay upon this guy, the stay, or shroud rope, 3, 4, is passed from thence through the window of the room below, and is there fixed.