904

THEORY AND PRACTICE OF ENGINEERING.

Rook 1L

Carpenter's Work for the upper Parts. — The planks laid on the centres for the constructionof vaults do not require any preparation at the yard, and therefore must be put at a dif-ferent price to that of the centres.

For the Labour of a Cube Metre of Planks, supposing the principals or ribs 2 inches dis-

tance, and the scantling 20 centimetres, we have 25 running inches for a cube metre.

Hours.

Piercing 13*5 holes in each, 20 centimetres long, making 2*70 metres at ar

hour per metre -

13*5 pins driving in at 00*6 hour for each -Putting in place -

Timber used for floors and other parts of wooden bridges require no other prepa-

ration at the yards than reducing them to their proper scantlings; they must be valuedaccordingly.

Labour on a Cube Metre of Joists, supposing the principals at 1 '5 metres distant, the scant-ling from 25 to 30 centimetres square, which gives 13’6 running metres to a cube metre,and 5 metres of length for the pieces, two of which will form the width of the bridge, eachrunning metre will comprise:

Hours of aCarpenter.

Two thirds of a notch at the meeting of the sleepers at the rate of 0-5

hour for each

- 0*33

Sawing the ends, having 0-15 metres square, at 5 hours per square metre - 0 75

\ of the joint at the other end, at I *30 hour4 wrought faces, 1*10 square metre at 1 hour2 small pins, driving at 006 hoursPutting in place or flxingWhich gives per cube metre

- 0*26 L 2-78

- 110

- 004

- 0-30

small pins, driving at 006 hours

- 37 -53

Laying the planks on the floors of wooden bridges may be valued in the same manneras in the platform for foundations.

Carriage of Timbers. — Large timbers are usually moved by means of a truck ; smaller,and planks, &c. are loaded on carts, &c. : when the distance is trifling, they may withadvantage be carried by hand: the price of this portion of labour is not subject to muchvariation. The proportion of price is always relative to the weight and size of the timbersmoved : —

For loadingUnloading

For going, &c., or returnin'distance of 100 metres

Hours of a truckserved by 10labourers.

Per cube metre

Waste upon Timber depends on the nature of the work, and the arrangements madebetween the merchant and contractor. Supposing the timber to be squared, the loss isthen divided into three portions: first, on the round timber, as it has been felled ; second,when squared or dressed on four sides, and reduced to a more regular figure: third, whensawn into planks and deals.

Round timber is seldom employed except for piles. The loss which is sustained on itarises from the length being usually greater than required ; something is cut from theextremities to form the head and point, and such timber loses three-fourths of its value. Thewaste may be estimated at one-tenth of the primitive volume.

The waste upon square timber depends on the nature of the works. It may be estimatedat one-eighth, which is near enough for timber prepared on its four faces, and at a tenthfor rough timbers of the primitive volume. If the works contain circular pieces it is rareto find timber crooked enough naturally ; regard must then be had to the waste sustained,and a price put accordingly. The waste on sawn timber is about an eighth of the volume,when the joints are wrought, and at a tenth when laid rough.

Waste on 2'imbers in temporary Constructions. —The cost of scaffolding centres and tem-porary bridges may, with respect to labour, be estimated in the manner before described ;the timber used is generally taken away by the contractor, and an allowance made to himfor the use and waste of one half. The diminution of value which timber sustains in theabove works arises from the change produced in the quality, and from the adaptation toparticular purposes, such as injury from piercing holes, mortices, &c.

Suppose a scaffold pile, five metres in length, cost 75 francs, and as the timber of this pilecut into lengths of a metre is only fit for fire-wood, its value would not be more than 25francs the cube metre, and diminishing the length of the pile from five metres to one, theprice of the cube metre will diminish in proportion.

Estimating, as above, one tenth tor the loss sustained in the pile for forming the headand point, which is abridging it one tenth of its length ; reducing it from 5 metres to 4 '5metres, which is the quantity it would be taken at in the estimate. When used, the head