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THEORY AND PRACTICE OF ENGINEERING.

Book IT.

Where it is determined that the walls shall occupy one-third of the section of a building,no figure is so well calculated for such a distribution as the equilateral triangle ; it enablesthe architect at once to limit and fix the proportions of his design; hence its universalapplication : and the mysterious qualities attached to it by the freemasons no doubt arosefrom the extraordinary facility it afforded them in setting out their several works. Whatcan be more simple or more beautiful than the distribution of this edifice ? Within a circlea hexagon is set out, the perpendicular sides of which mark the outer faces of the buttresses;the junctions of the angles, by forming a base to every two sides, produce the twoequilateral triangles, which sub-divided not only enable us to arrange the other portionsaccurately, but also to measure with the greatest nicety their relative dimensions. Thequantities of material employed in construction can be estimated by such means muchmore easily than by measuring each portion separately, cubing it, and adding the numerousdimensions so obtained together ; there is decidedly more simplicity in the former than inthe latter system: the area of one triangle being found, we at once know that of all the rest,

Fig.3008.

CHAPTER-HOUSE, WELLS: PLAN.

or of any portion. In the subject before us the distance from the middle of one buttress tothat of the other is 31 feet 6 inches, and the diameter taken through them at this level is92 feet; omitting the buttresses, the outer side measures 26 feet, and the inner 2] teet6 inches, the respective radii of the circles which comprise the octangular outer walls andthe void being 38 feet and 31 feet 5 inches. Hence we find that the entire area of thebuilding without the buttress is - 3264 feet.

The area of the void ------ 2176 feet.

And of the walls or points of support - 1088 feet.

At the level of the crypt, above the outer plinth, we have these regular proportions, two-thirds void and one-third walls.

The height of the entire building, from the pavement to the top of the parapet, is 72 feet6 inches, and to the top of the pinnacles 92 feet, the total height being equal to the extremediameter taken above the plinth moulding on the outside. The interior of this chapter-