" Upon the 11th, I again went out in the vessel that con tained the remaining pieces of Course VI.: those I saw fixed ; and that course, consisting of thirty-two pieces, closed in the same evening. (See Plate III.) This completing our six base ment courses, brought our work upon the same level to which we had, the preceding season, reduced the top of the ruck ; and upon this, as a common base, the rest of the struc ture was to be raised by regular entire courses. The time this part of the work (consisting of one hundred and went v three pieces of stone) had taken up, was from the 12th of June to the 11th of August inclusive, being a space of sixty one days. We now considered our greatest difficulties to be successfully surmounted, as every succeeding course had given us more and more time, as well as more and more room ; and this will appear from our proceedings ; for it has already been noticed, that the two first courses, consisting of nineteen pieces of stone only, had cost us seventeen days.
" Having now got the work to this desirable situation, I apprehend it will be agreeable to my reader to be more par ticularly acquainted with the method in a Ilia the stones were set and fixed. I have intimated, that when each separate piece, of which a course was to consist, was separately W ro ugh t, they were all to be brought to their exact places with respect to each other, upon the platform in the work-y ard, and so marked, that, after being numbered and taken to pieces, they could again be restored to the same relative position. This was done upon the circular courses by drawing lines from the centre to the circumference. passing thr(nigh the middle of each set of stones; and likewise concentric cir cles through the middle of each tier or circle of stones, so as to indicate to the eye their relative position to each other : but to render the marks not easily delible, where those lines crossed the joints, a nick was cut and sunk into the surface of the two adjacent stones; for doing which, a piece of thin plate-iron was employed, with sand, upon the principle that stones are sawn ; so that not only the sight, but feeling, could be employed in bringing them together again exactly ; for the same or a similar plate being applied to the nick, the. least irregularity of its position would be discoverable. In a similar manner the stones of the base courses were marked by lines drawn parallel to the length of the steps, and others perpendicular to the same, the crossing.; being sawn in, as beli,re described. There was, however, a nicety in this part of the work, that required particular attention, and that was in forming a provision for setting the four radical stones, that occupy the four radical dovetails into which each step was formed, as may be observed in the several figures of Plate III. Those stone; were formed, from the work of the rock's being actually moulded off and from the trimmer, already de•.e; died, of bringing those moulds to agree after they were home from the rock, those stones were laid upon the platfonn thereby, and then marked with lines upon their own substance, in the manner just mentioned: and as the distances of each of those stones were then ascertained by gauge-rods of white fir-wood, while upon the platform ; it must be expected, as each step was reduced to a level plain, as the platform was, that when laid upon the rock in their clue positions and distances, by the gauge-rods., they would
nearly fit the dovetails that had been cut in the rock to receive them ; and where there was the least want of fitness, as might possibly happen with bodies of so rigid a nature, either the stone or the rock was cut, till each stone would come into its exact relative position, and then all the rest would follow one another by their marks, in the same manner as they had done upon the platform.
" It is necessary to be noticed, that the waist of each piece of stone had two grooves cut, from the top to the bottom of the course, of an inch in depth, and three inches in width : applicable to those grooves were prepared a number of oak wedges, somewhat less than three inches in breadth, than one inch thick at the head, nearly three-eighths thick at the point, and six inches long. The disposition of these grooves is shown in the courses of Plate III. where the little black parallelogram figures, placed along the lines describing the joints of the courses, represent the tops of the grooves, and their place on the right hand or left of the joint line show in which stone the groove is cut. It is also to be noted, that where the flank side of a stone was not more in length than a foot, or fourteen inches, one groove was generally deemed sufficient ; hut those of eighteen inches or upwards had, generally, in themselves or the adjoining stone, a couple of grooves.
" The mortar was prepared for use by being beat in a very strong woolen bucket, made for the purpose ; each mortar beater had his own bucket, which he placed upon any level part of the work, and with a kind of rain mer, or wooden pestle, first heat the lime alone, about a quarter of a peek at a time, to which, when formed into a complete, but rather thin paste, with sea-wate•, hc then gradually added the other ingredient, keeping it constantly in a degree of toughness by continuance of heating. When a stone had been fitted and ready for setting, he whose mortar had been longest in beating came first, and the rest in order: the mason took the mortar out of the bucket ; anti, if' any was spared, he still kept on beating; if the whole was exhausted, he began upon a fresh batch. The were first tiled, and heaved into and out of their recesses, by a light movable, triangle, which being furnished with a light double tackle, the greatest number of all the pieces could be purchased by the simple application of the hand ; and this nettle our stones to he readily manageable by such machinery as could commodiously be moved and carried back ward and forward in the yawls every tide. To the first stone, and sonic few others, we took the great tackle, that we might hoist and lower them with certainty and ease ; but there were not in the whole above a dozen stones that required it.