E D D

332

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ticular figure.—Connected with its roots, which lie hid belowground, it rises from the surface thereof with a large swell-ing base, which at the height of one diameter is generallyreduced by an elegant curve, concave to the eye, to a dia-meter less by at least one-third, and sometimes to half of itsoriginal base. From thence its taper diminishing more slowly,its sides, by degrees, come into a perpendicular, and for someheight form a cylinder. After that, a preparation of more cir-cumference becomes necessary, for the strong insertion andestablishment of the principal boughs, which produces aswelling of its diameter. Now, we can hardly doubt but thatevery section of the tree is nearly of an equal strength inproportion to what it has to resist: and were we to lop offits principal boughs, and expose it in that state to a rapid cur-rent of water, we should find it as much capable of resistingthe action of the heavier fluid, when divested of the greatestpart of its clothing, as it was that of the lighter, when all itsspreading ornaments were exposed to the fury of the wind :and hence we may derive an idea of what the proper shapeof a column of the greatest stability ought to be, to resist theaction of external violence, when the quantity of matter isgiven whereof it is to be composed.

“ In Plate V. Figure 1, is a sketch, representing the ideawhich I formed of this subject. It is farther observable, inthe insertions of the boughs of trees into the bole, or of thebranches into the boughs, (which is generally at an obliqueangle) that those insertions are made by a swelling curve, ofthe same nature as that wherewith the tree rises out of theground ; and that the greatest rake or sweep of this curve isthat which fills up the obtuse angle ; while the acute angleis filled up with a much quicker curve, or sweep of a lessradius : and Figure 2, of the same Plate, represents my con-ception of this matter. In this view of the subject, I imme-diately rough-turned a piece of wood, with a small degree oftapering above ; and leaving matter enough below, I fitted itto the oblique surface of a block of wood, somewhat resem-bling the sloping surface of the Eddystone rock; and soonfound, that by reconciling curves, I could adopt every part ofthe base upon the rock to the regularly turned tapering body,and so as to make a figure not ungraceful; and at the sametime carrying the idea of great firmness and solidity.

* The next thing was to consider how the blocks of stonecould be bonded to the rock, and to one another, in so firma manner, as that, not only the whole together, but every indi-vidual piece, when connected with what preceded, should beproof against the greatest violence of the sea.

“ Cramping, as generally performed, amounts to no morethan a bond upon the upper surface of a course of stone,without having any direct power to hold a stone down, incase of its being lifted upward by an action greater than itsown weight ; as might be expected frequently to happen atthe Eddystone, whenever the mortar of the ground-bed it wasset upon was washed out of the joint, when attacked by thesea before it had time to harden; and though upright cramps,to confine the stones down to the course below, might in somedegree answer this end, yet, as this must be done to eachindividual stone, the quantity of iron, and the great troubleand loss of time that would necessarily attend this method,would in reality render it impracticable ; for it appeared, thatMr. Winstanley had found the fixing twelve great irons, andMr. Rudyerd thirty-five, attended with such a consumption oftime (which arose, in a great measure, from the difficultyof getting and keeping the holes dry, so as to admit of thepouring in of melted lead) that any method which requiredstill much more, in putting the work together upon the rock,would inevitably, and to a very great degree, procrastinatethe completion of the building. It therefore seemed of the

aritity 1

utmost consequence to avoid this, even by any <1 f 0 r ' ts ,time and moderate expense, that might be necess 0

performance on shore; provided it prevented hm tb erebusiness upon the rock: because of time upon the r a v ef/was likely to be a great scarcity, but on the s' (0sufficient plenty. This made me turn my though ] ) o"'

' In

‘.tio»

could be done in the way of dovetailing,ever, of this as a term of art, I must observe.

that d

9 \ir r

principally applied to works of carpentry : its a PP - n g ;the masonry way had been but very slight anl f P eU letin regard to the small pieces of stone that had gS) a"with a double dovetail, across the joint of larger in( r ^generally to save iron, it was a kind of work n0 t retfi} gobjectionable than cramping; for though it would^ con5 ist'®melted lead, yet being only a superficial bond, an jjjjely jof far more brittle materials than iron, it was n ^ J l' 9 ^answer our end at all. Somewhat more to my P u ^( 3 0 f I 0 ®occasionally observed, in many places in the str ( j ie lo edon, that, in fixing the kirbs of the walking-pa 1 j( e£l( Jei' s ’pieces, or stretchers, were retained between two ad"Pbond pieces ; whose heads being cut dovetail'W e*P^themselves to, and confined in, the stretchers ’ ) a( j ) iie v ,,dient, though chiefly intended to save iron an< ^ ®

theless appeared to me capable of more firnin a t 1 .superficial fastening could be ; as the tye was !} 3 ^ afl ted > j e ,bottom as at the tgp, which was the very thing sin a if

therefore if the tail of the header was made would in ftbequate bond with the interior parts, the woik ' . ll3 b) . i

be perfect. What I mean will be rendered o t ),is a 1 jinspection of Figure 3, in Plate V. Somethmg^^jp t ioH^ eI also remembered to have seen inBelidors wb eI ' e i e ifthe stone floor of the great sluice at Cherburgji^ ^ g{ ttails of the upright headers are cut into dove a ^ oJii t ^insertion into the mass of rough masonry belo' '^ oC ks ll ' e .beginnings I was readily led to think, that it j 1 j a rg e a a ti'selves were, both inside and out, all formed m 0 l>®tails, they might be managed so as mutually to the , 0 cfeother together; being primarily engrafted in ^ tl> e ^ t -gnin the round and entire courses, above the ^to, 0118 . e d 11they might all proceed from, and be loeke j prod^jctcentre stone. After some trials in the roug^i jpe ^ fl rcomplete design, of which Figure 5, Flute ’ ge% t ah 0 ' ^copy ; the dotted lines representing the course gatD e c ®below, which in the original was drawn from Qn ea con the other side of the paper ; so that 1°° 1 ° 0 r,separately, each course was seen distinc I^ rgeS , s' 1 r l tthrough the paper, the relation of the two ® ^ % viis c j . s ae | *how they mutually broke joint upon one an0 . n V :lS P U ^ v oi'^j

pointed out: and this method of represents er ,plat® t te<»throughout; but not being practicable in c °Pg t [ )0 d W f tl ,eI am under the necessity of introducing the p u sioUlines, though attended with some degree o . fl ,]iil e

main design. „ Joveto'^f’g st e ? 9

“ It is obvious, that in this method o tt jng f '„\\l ^the slope of the rock was making good ; 7 .j jt

(formed by Mr. Rudyerd) also into doven rC e»b 0 nIJsaid, that the foundation-stones of every cour n ^ fli

into, or rather rooted in, the rock ;keep all the stones in onecourses themselves (asupon each other. But after losin

which

but

course together, or

one stone) from JJJo *

fb° ve it ; then , hold of the rock, by ^

be bonded in the eVe, 7 sto ne in the same c ° ur , rnnght be consider J ron Sest manner with everywould weio-h a Ied -? s coa 8isting of a single st ° n % a ld befarther retained enable number of tons, and *

wi ‘en completed tl W Soor below b 7 the cemen ’ « » P

P eUid > the sea would bare no action