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call it 1, the 1 in the middle will be 10, the other figureswhich follow will be 20, 30, &c., and the 10 at the right-hand end will be 100. If the first, or left-hand unit becalled 10, the middle 1 will be 100, and the following figureswill be 200, 300, 400, &c. and the 10 at the right-hand endwill be 1000; and thus, whatever be the value of the firstunit, the second unit in the middle is always ten timesgreater; and whatever is the value of the first and secondunit, the following numbers to the right denote so manytimes that value as the number expresses.

The fourth line, d, called the girt line, is a single line,proceeding from 4 to 40. Upon it are marked w G at17'15, and AG at 18 "95, the wine and ale gauge points, tomake it serve the purpose of a gauging-rule.

The use of the double lines, A and b, is for working therule of proportion, and finding the areas of plane figures.And the use of the girt line d, and the other double line c, isfor measuring of timber. On the other part of this side ofthe rule, there is a table of the value of a load, or 50 cubicfeet, of timber, at all prices, from sixpence to twenty-fourpence, or two shillings, per foot.

On the other side of the rule are several plane scales,divided into 12th parts, marked inch, f, 1, &c. signifyingthat the inch, J inch, &c. are each divided into 12 parts.These scales are useful for planning dimensions that aretaken in feet and inches. The edge of the rule is dividedinto inches, and each of these inches into eight parts, repre-senting half inches, quarter inches, and half quarters.

In this description, the rule is supposed to be folded; letit now be opened, and pull out the slider, you will find theback of it divided like the edge of the rule, so that altogetherit will measure one yard, or three feet, in length. Theslide is very useful in taking inside dimensions for anylength not less than one foot, nor greater than three feet.

Some rules have other scales and tables upon them; as atable of board measure, one of timber measure, a line forshowing what length for any breadth will make a foot square,also a line showing what length for any thickness will makea solid foot. The former line serves to complete the tableof board measure, and the latter the table of timbermeasure.

The thickness of the rule is generally about a quarter ofan inch ; this face is divided into inches and tenths, and num-bered, when the rule is opened, from the right-hand towardsthe left, 10, 20, 30, &c. to 100, which falls upon the joint,j The other half is numbered in the same manner, and theI same way. The scales serve for taking dimensions in feet,tenths, and hundredths of a foot, when the contents are foundby decimals.

Carpenter’s Square, a square, of which both stock andblade consist of an iron plate, of one piece ; it is in sizeand construction as follows:—one leg is 18 inches in length,numbered on the outer edge, from the exterior angle, withthe bottom of the figures adjacent to the interior edge : theother leg is 12 inches long, and numbered from the extre-mity towards the angle; the figures are read from theinternal,angle, as on the other side; each of the legs is aboutan inch broad. This implement is not only used as a square,but also as a level and measuring rule. Its application as asquare, in taking measures, is so easy as not to require ex-ample ; but its use in taking angles may be thus illustrated :suppose it were required to take the angle which the heel ofa rafter makes with the back; apply the end of the shortleg of the square to the point of the heel and back, with theedge of the square level across the plate; extend a chalk linefrom the ridge of the roof to the said heel-point, and thedivision on the perpendicular leg of the square which the line

falls upon, will mark the inches, and show how far it deviatesfrom the square in 12 inches.

Carpenter’s Work, in the mensuration of artificers’ work,includes the taking of the dimensions of every description oftimber necessary in the construction of buildings, finding theircontents, and valuing the same.

The works done by the carpenter, in the general construc-tion of buildings, are the preparation of piles, sleepers, andplanking, or other large timbers in the foundations, center-ings to vaults, wall-plates, lintels, and bond-timbers, nakedflooring, partitioning, roofing, battening to walls, ribbed ceil-ings to form vaulting for lath and plaster, &c. These arenot necessarily used in the construction of every edifice: pilingand planking, or other timbers used in the foundation, areonly incidental, depending upon the insufficiency of theground to be built upon; the remaining articles may beall used in the most substantial and elegantly constructedhouses.

Large and plain articles, where a uniform quantity ofmaterials and workmanship is expended, are generally mea-sured by the square of 100 superficial feet.

Piles may be made at per piece, and driven by the footrun, according to their diameter, and the quality of theground.

Sleepers and planking are measured and valued by takingthe superficial contents in yards or squares.

Plain centering is measured by the square; but as theribband boarding are two different qualities of work, theyought to be measured and valued separately; one dimensionof the boarding is taken by girting it round the arch, theother is the length of the vault.

Centering for groins should be measured and valued ascommon centering, but in addition thereto, the angles shouldbe paid for by the foot run, over and above; that is, the ribsand boarding ought to be measured and valued separately)according to the exact superficial contents of each, and theangles by the lineal foot for workmanship in fitting the ribsand boards, and for the waste of wood occasioned by theoperation. Wall-plates, lintels, and bond-timbers, are mea-sured by the cubic foot, under the denomination of fir-in'hand.

Naked flooring may either be measured and valued by thesquare, or by the cubic foot, according to the description otthe work, and the quantity of timber employed. In formingan idea of its value, it is proper to observe, that in equalcubic quantities of small and large timbers, the small timberswill have a greater superficies than the large ones, and there-fore the saving will not be in a ratio with the solid contents >consequently the value of the workmanship will not follow thecubic quantity or said ratio. The difficulty of handling tim*hers of the same length increases with the weight or solidity’as the greater quantity requires greater power to handle ihand consequently a greater expenditure of time : and thoughthe time may not be exactly in a ratio with the solid quantity’there will be no great difference, as the respective sections w 11not vary considerably in their dimensions; and as the value othe sawing upon a cubic foot is comparatively small to that othe work done by the carpenter, the whole value of labourand materials may be ascertained with sufficient accuracywhere the work is uniformly of one description.

In naked flooring, where girders are introduced, thejinterrupt the uniformity of the work by mortises and tenon®"In this respect, the price ascertained by the cubic quanti yof the girders, would not be sufficient at the same rate Pfoot, as the other parts, not only on account of the greatference of size, but as it is cut full of mortises to recel g rthe tenons of the binding-joists, it occasions a still gi’ ea