EDD

350

EDD

figure distinctly shows the method of salvagee strapping ;being double, that the pins being readily knocked out, theycould be frequently greased without trouble.

“ A T .B. The shears, blocks, and tackles, used at Mill Bay,were nearly the same as at the rock ; and one pair of maintackle blocks at each place, with the same pulleys, wentthough the whole service ; but the pins were renewed eachseason, and sometimes oftener, being of wood, on account ofthe salt-water ; but were frequently greased. The maintackle-fall at each place was no larger a rope than of threeinches circumference ; being a white rope, remarkably softlaid, hauser-fashion ; and which is of material consequence.

“ Plate VIII.— Descriptions of supplemental matters,haring reference to the Eddystone building.

“ Figure 1. An upright front view of the great tackle, orpurchase-blocks of twenty sheaves, or pulleys.

“ Figure 2. A side view of the same blocks, referring toFigure 1. The advantage of this construction is, that thetackle-fall, or running-rope, may be reeved through thetwenty sheaves, without a cross or interference; so thatthe standing part, or beginning, may be in the middle of theupper block: and the ending, hauling part, or fall, uponthe middle pulley of the same block. The weight thereforebeing suspended by twenty ropes instead of six, as in commontriple-blocks, the tackle-fall, as relative to a given weight,may be lesser, or of fewer yarns in the same proportion ;which renders the whole much more flexible and pliant, andwhich, together with the advantage derived from the modeof reeving, occasions their rising and falling nearly upon aparallel. Beginning in the middle, the greater sheaves arereeved as far as can be on them; from thence going to thefirst of the smaller sheaves, and reeving the whole of themthroughout, you then go to the first of the greater sheaves,before left unreeved, ending upon the middle sheave of theupper block; and thus arises a diminution of the frictionfrom the more equal distribution thereof.

“ Figure 3. An upright section of the store-room, toan enlarged scale; in it is shown the centre whereonthe upper store-room floor was turned; and in like mannerthe rest.

“ Figure 4. The plan relative thereto, the letters beingcommon to both.

“a b, c d. Two of the sixteen ribs, formed to the circleof the vaults of the floors. These ribs are connected at theirends by two wooden rings, ef gh i k; the former supportedby four posts, three of which are shown in their places, andthe latter by eight; of which only one is shown on the righthand, and one on the left, to avoid confusion. The rings areeach made to take asunder, that after striking the centrethey might be got out of the room.

“ At 11, m m, two of the ribs are supposed taken out,to show their bearings upon the rings; they were opencentres, that it might be seen underneath when the jointswere fair.

“Figure 7, of Plate IV., shows how the sixteen radii ofstones would apply to the sixteen ribs. In this plan,Figure 4, a shows the well-hole, and b b the cross timbersfor supporting the four middle posts, whose places are markedout by dotted little squares.

“ Figure 5. An elevation, and Figure 6, the relative planof a dial stone, taken professedly from the general figure ofthe Eddystone lighthouse ; being the design of the lateJames, Duke of Queensberry, and by him erected at Ames-bury, Wilts, with a dial upon it, by Mr. Ramsden. Thedrawing, of which this is a copy, was given me by the Duke;and is placed here as an instance, that the Eddystone columnmay be applied to some uses of architecture.

“Figure 7. One of the silver medals given to* e °as a token of the service. got U P

“ Figure 8. The tool wherewith the stones werfrom the bottom of the gut.

‘ A. One of the stones, with two trenail holes.

“ Suppose this stone lying flat in the bottom^ ^

of

ub

the side a uppermost. The tool has a pole or

Thisto ho

ffle

sing'

thf uS *

being

twelve feet long, sufficient to reach the bottom,prong, c, is forged to a very gentle taper, such aseight or nine inches into a trenail hole, (all of * *®.jj f-ist >bored to a gauge) it can be driven by the P°' e > f gravityobserving that the arm e corresponds to the centre b toof the stone. The water is generally so clear as ^ bethe bottom ; and, in case of any ruffle by the tvn^ >^ r0l) gbin a great measure freed from agitation, by looking ^ tena speaking trumpet, whose mouth is put downinches into the water. The rope d ef | being th e j en gtbby the main tackle, instead of its drawing out, the °j,ole!the arm g causes the prong to jamb the faster in gj^defand the staff being quitted by the hand, with a cor tb®

its flying off too far, the whole assumes the P osltl g re d in* 0figure; and, when brought above water, is 1°'

a yawl.

“ Figure 9. A section of one of the mortarin it the beater.

buckets)

an 0

. me nearer. 1ant erI18

Figure 10. One of the internal faces of 11® ^ ^er®glass frames, and therein the cross bars of iron, as bah

actually fixed. Besides the flat at each end o tb®

distinguished by a darker shade, and through ^ | IlC b, s °screws passed ; each end was also cranked about a^ c0 pp® fas to set the transverse part of the bars clear o ^ tb® lfsash-frame; and they were cleared of each ot i® otb^intersection, by one of them being made straigj 1 > tb®curved in that part. All the panes being , el w ben ^candles, the chandelier rings are so hung, t' ia ^ c lifl acandles are at rest, dispensing their light, that o ^ 0 f tbdelier passes through the range of panes A, an gn u0® ’other through the range B; and when the candles r a og e ’

one of the rings of lights being seen throughthe other mounts to D, and vice versa. "Rdt'} 3 .a

“ Figure 11. The chain of triangles, from t ie gcer tainb ,£ ’to the flag-staff of the garrison of Plymouth, fd atheir distance trigonometrically. , „,;thin *

“ Figure 12. An enlargement of the tvorheadlands of the Sound. . being

“The whole country about Plymouth ® OI ? n tter , tha n ^uneven, I could not readily obtain a base n ta ki»g 1 gvery carefully measuring the two lines B G, B > y q '

the right line ® ^

the tie® 1,6 ,

suppose to err more than half a foot. Agai^ cob 11 ^place from whence the two beacons, tv, G, coU _ an( j alldiously seen for the purpose, was the S ’j, e ca r ® uthree angles of the triangle W S G, being *’ ‘, e ' til ken trU !fJietaken, I conclude the angle w s g = 10 f ’ g \e. ..a minute; that is, to yi-»d part of the wh , a pa

-.1-1 therefore be determined wflh.n

of tlie .' vh g 0 che.nf>‘Jd

j - --J —— **•© - ‘it tin©

intercepted angle wbg; whence the ngnt *obtained, making a base of 1871 feet, and 'X 1IC t i lf

line s w couldwhich being considered as a new basebe esteemed true within 6 ^th partthis, and the angles taken as

SCI'*',

marked upon ^ olM]1 jne<l)

to®®’

lines w P, W M, and W E, were successively ® jjddy 81 .finally f e, the distance of the flag-staff ftj (,m p oUr tee n I p 0 ol)came out very near, but somewhat less, than g u tton . at>But the interior harbour of Plymouth, ca ^jjygton® e pbeing about three furlongs farther from f°°

the flag-staff, the whole distance may

be estee® e

miles and a quarter from Plymouth harbour.