Chap. X.

VALUE OF ARTIFICERS’ WORKS.

909

T' = (l +“ T):

T = the time of cutting the face straight.

T' = the time of cutting a curved face.r = the radius of curve of the surface of this facing.m = 0*75.

Then the price of the curved facing will require the time necessary to reduce the stone toa plane face and a curved one. But if the reducing has for its object the execution of someparts in projection, as obtuse angles or retreats, it cannot be valued as if cutting a face ;but an allowance of ten times the labour is required for mere plain work : after cutting theface, the beds and joints require the next consideration : both are valued at the sameprice, which is an erroneous system; the joints requiring much more reducing than thebeds.

For cutting the jointsthe beds

of the time necessary forcutting the face.

Cutting mouldings for cornices is valued thus, a price for reducing the stone, and after-wards according to the girth of the mouldings, as moulded work : other expenses areincurred in cutting stone besides the labour, as tools and oil, &c. ; for cutting granite, tenpoints are allowed for every square metre for the calcareous stones : this expense is trifling.

Stone suffers a waste, which varies from a tenth to a fourth. The carriage is performedby a truck, or low waggon, drawn either by men or horses.

Supposing the specific gravity of stone to be 2, a man can draw 0055 cube metres, andsix men are required to load and unload the blocks of stone ; these six men will be suf-ficient for the service of the truck, when the volume of the stone does not exceed 0*38 cubemetres; if the stones are heavier, a greater number of labourers must be employed, whowill lose their time after loading, unloading, and during their return; and as it costsmore to move a truck with men than with horses, there is a point where, relative to theweight, it becomes preferable to use the latter. The volume of stone that may be drawnby a horse being 0*4 cube metres, it is easy to determine the size of the stones which re-quire one or more horses, and

When the stone is between 0*60 and 0*80 cube metres 1 horse

0*89 and 1*181 -29 and l -581 *69 and 1 *98

2 do.

3 do.

4 do.

Upon this basis the charge for transport may be easily obtained, when the time of loadingand unloading is also known, which is in proportion to the dimensions of the stone ; an houris required for a block for every cube metre; and the time necessary for going and re-turning are 100 metres, 0*6 hour.

When the stone arrives, the masons receive it, and sometimes it is requisite to move it bymachines when a block is 0 75 metres cube, and it is required to be raised 8 metres; for at-taching and detaching the tackle, 0*50 hours is allowed for two men and six boys.

For mounting to 8 metres at the rate of 0*1 hour per metre, 0*80; the same number ofmen and boys being employed. To bed the stone requires a mason, two assistants, and alabourer: when great rapidity is necessary, there are in addition two others to lay thecement, and an additional labourer.

For a cube metre 1 for the placing - - 3 *001 hours of a mason, 2 assist-

of stone. J fqr the grouting - - 2*00 J ants, and a labourer.

It is not necessary to add anything for the construction of vaults ; the experiments madeat the bridge of Nemours indicated that placing the voussoirs is less costly than that ofthe courses of the facings of walls; bedding the cube metre of stone at this bridge requiredfor the piers 2*94, for the abutments 3*, and for the vaults 2*67 hours. The quantity ofmortar required varies from a tenth to a twentieth of the volume of the masonry.

After the work is done, the stone requires re-dressing and pointing, which ordinarilyamounts to about a twentieth of the primitive cutting ; a running metre of joint occupieshalf an hour for a mason and labourer; the mortar used in the joints may be estimated at0*001 cube metre.

Beton . — The preparation of various species, and of mortar used for composing the backsof vaults, may be estimated in the same way as moellon : with regard to beton, someallowance must be made when it is thrown from a height into the water ; the labour isabout the same as that for throwing earth with a shovel,or stones for foundations: where itis thrown into an inclosure with ease, an allowance must be made.

The covering of the backs of arches of bridges is so important for their preservation, thatgreat care should be used. The labour to spread and level each layer should be valuedfor a cube metre at 4*5 hours of a mason, served by a labourer; and that of the beating atI *5 hours of a labourer for every square metre of each of the layers beaten. The labour