Plans, Elevations, And Sections. The various structures, and parts of structures, met with in building construction, are solids, having length, breadth, and thickness, and sides more or less numerous, according to their form. The paper on which the drawings connected with building construction are made, having only surface, that is, length and breadth, some method of representing upon a flat surface the form of solids, so as to show each side and the peculiarities in construction dependent on, or connected with, that side is obviously required. The delineation upon paper of an object which is a solid is, technically speaking, a " projection;" and the peculiar method of projection employed in building construction is called "orthographic projection." For the principles of this, and other kinds of projection, as " isomet-rical," the pupil is referred to the volume in this series on Plane and Solid Geometry. The projection of any body taken on a line parallel to its base, or as viewed when looking down upon it in the direction of a line at right angles to its surface, is called a "plan," as fig. 4, Plate II., which may be supposed to represent the plan of a house, or of a box with the lid or top taken off. Plans of houses, in reality, " horizontal sections," taken on a line, at a distance a little above the ground level, which line is parallel to the base. A "section" is the view of an object, representing it as it is supposed to appear, when it is cut either horizontally or vertically by a line parallel to any given line in the plan. Thus, fig. 4, Plate XXXVIIIb., may be taken as a "horizontal section," on the line a b, in fig. 5, Plate XXXYIIIb., showing the thickness of the walls of the house, or the thickness of the sides of the box, as the case may be. The section in fig. 6, Plate XXXYIIIb., is called a "longitudinal section," or a " longitudinal vertical section," on the line a b in the plan, fig. 4, Plate XXXYIIIb., this line being parallel to the front and back lines. If the section was taken on the line c d, fig. 4, Plate XXXVIIIb., the section would be called a "transverse or cross section," or a "transverse vertical section." "Elevations" are views of the vertical or standing part of objects, and are called "front elevations," "back elevations," "end elevations," or "side elevations," according to the side from which the object is viewed; the point of view being taken from a point at right angles to the surface of the front, back, end, or side of the object. Thus, fig. 5, Plate XXXVIIIb., is a front elevation, and gives the height of the openings e,f, and g, in plan, fig. 4, Plate XXXVIIIb., the breadth of which only is there given; fig. 7, Plate XXXVIII&., is the "end elevation," A, fig. 4; fig. 8, Plate XXXVIIIb., the "end elevation," B, fig. 4, Plate XXXVIIIb. If the object were a house, these two end elevations would be distinguished by the points of the compass to which they looked, as " west-end elevation," "east-end elevation." The "back elevations" of fig. 4, Plate XXXVIIIa., will be the same as fig. 5, omitting the openings e and f, with the opening g, the same as in fig. 5, Plate XXXVIIIb. Where there are peculiarities in the back part different from the front part of any object, a back elevation would be necessary. The pupil desirous further to pursue the subject of drawings is referred to the volume noted in p. 14. But we give a few examples of a simple kind to show methods of copying and laying down drawings. Infig. 9, Plate XXXVIIIb, we give a drawing showing a "front elevation" of a building, of which, in fig. 10, we give part "ground plan." The two drawings are placed in relation to each other to show the method of taking the lines of an elevation from the distance given in the ground plan, and vice versa. A glance at the two figures 9 and 10, in Plate XXXVlllb., will show this; the dotted lines being carried up from the plan to give the lines of front elevation, or cairied down from the elevation to give the lines of the plan. The letters of the two diagrams, figs. 9 and 10, show corresponding parts; and the pupil, by a study of these should be able to understand, to see the principle of the method adopted, and be able to apply it to other subjects of a like nature. In Plate XXXVIIIc, fig. 1, we give a diagram showing the method of " laying down " or " setting out," the principal lines of the elevation of building in fig. 9, Plate XXXVIIIb The line a b, fig. 1, Plate XXXVIIIc, is first drawn as the "ground line" or "base line." Near the centre of this line, as at the point c, a line c d is drawn at right angles to a b. This is the main "centre line" of the building, and corresponds to the line k I, in fig. 9, Plate XXXVIIIc From c the distances ce, eg (equal to the distance of centre lines ran, op,fig. 9, Plate XXXVIIIc) are set off; and lines ef, g h, are drawn parallel to cd; these give the centres of the side wings, ab,cd, fig. 9, Plate XXXVIIIb. The heights of the points r, s, t (taken from the copy of the drawing in fig. 1, Plate XXXVIIIc, being to a larger scale than that in fig. 9, Plate XXXVIII6.), are then to be set off from the base line a b, fig. 1, Plate XXXVIIIc, to the points f, h, d, and b, and lightly pencilled lines drawn through these, parallel to the base line a b. The distance of the terminating lines of these lines on each side of the centre line, po, kl, mn, fig. 9, Plate XXXVIIIb., should then be taken and set off from points f h and d, on both sides of the centre lines ef, c d and g h, this will give the width of the respective parts. The heights of the top and bottom lines of windows, as i and e,fig. 9, Plate XXXVIIIc, should then be taken and set off in the lines, ef, gh, fig. 1, Plate XXXVIIIc, to the points mn, op, and through these points lines drawn parallel to a b, the full lines show the parts when inked in, the dotted lines represent the lightly pencilled in lines at the first operation. Fig. 2, Plate XXXVIlla., is an enlarged sketch of the window e, in fig. 9, Plate XXXVIIIb., showing the method of drawing it. First, draw a "centre line,"a b, and a "base line," c d, at right angles to this; then set off the various heights, as b, e, and/, those taken from the copy, or the scale according to dimensions given. Then take half the width of opening and set this distance off, on each side of the centre line, a b, to the points g and h; then draw parallel to a b lines gk, hi, making the line drawn through/parallel to cd. Measure next to the end s c d , and draw l c, m n parallel to a b. Fig. 3 shows the lines required to draw the door in fig. 6, Plate XXXVIIIb., fig. 4 being an enlarged sketch, showing the method of putting in the panels; in this, a b is the "centre line" of the door, corresponding to a b in fig. 3, and the line ed, fig. 4, Plate XXXVIIIc, gives the top line of panels, the widths of the panels being set off from the point a, to e and /. Fig. 5 shows the method of drawing a pediment terminating a roof. The line a b gives the upper line of last number of the cornice, and c e the centre line of roof; from b, set off the height b c, measure from a to d, and join cd. Fig. 6, Plate XXXVIIIb., is a front elevation of a house, the leading lines of which are given in fig. 7, showing the method of commencing the drawing; fig. 8, Plate XXXVIIIb., is pediment of door; fig. 9, drawing, enlarged, of chimney stalk, and fig. 10 shows the method of drawing in the "quoins;" the distance, ab, being divided into nine equal parts, and lines drawn through them parallel to c d; the line a b is the outside boundary line, and the projections of the quoin stones inward from this are given by measuring from the point e to f and g ; and drawing from these, lightly pencilled in lines, the intersection of which, with the lines drawn through the points 1, 2, 3, etc., parallel to c d, give the widths or breadths of the quoins.

8. As forming a practical exemplification of the connection of plans, elevations, and sections, with one another, we give, in Plates XXXVIIId, XXXVIIIe., and XXXVIIIf, a set of "plans" of a cottage villa. The student should carefully note the connection of one drawing with another, so as to be able to lay down in elevation from a plan, etc., taking the measurements in order. The plans, elevations, and sections, form what is called a "set" of drawings, but in addition to these a number of other drawings are also prepared; these, as already stated in a previous paragraph, are known as " details or " detailed drawings," which, in number and elaboration of finish, vary according as the architect may consider necessary, or as the builder or contractor may require.

9. These detail drawings, when commencing anything of an elaborate character, in which the lines and parts are numerous and complicated, are of course drawn in the manner and by the aid of all the appliances already described. But in a great many instances, the architect is often, while " upon the ground," called upon to furnish the workmen quickly with "free-hand sketches" of various parts, which, while yielding no pretensions to accuracy of measurement of these parts, or even of drawing, serve nevertheless to afford to the workmen the necessary information as to the form of the part required, and as no "scale" can, of course, be given, the dimensions are simply marked upon the sketches, as in figs. 1, 2, and 3, Plate XXXVIIIg. Free-hand sketches of various parts, for the guidance of workmen, do not require to be finely executed, they must of course indicate accurately the form or outline and the connection of the various parts. There are some draughtsmen, however, who have a wonderful facility in executing sketches which, although called "rough," possess all the accuracy and finish of work done carefully in the study. Not many, however, possess this ready faculty; and although its possession is greatly to be desired, a less perfect capacity will be found useful enough for every-day work. "While a facility to execute rough free-hand sketches of various parts is useful to the practical man in preparing drawings of parts which require the instant attention of the workman, the converse is of course of equal utility to the practical man, in enabling him to take sketches on the spot, from which afterwards, in the quietness of his study, he can prepare finished drawings; care being taken to mark all the dimensions in their proper places. Enough - in connection with which the student will find in other works of this series - has been said on the subject of drawing to enable the student to gather up its chief principles; and to induce him to devote that time to their fuller study, or the special works devoted to their elucidation, which will impart to him the knowledge necessary in following out the pursuits to which he may have devoted his career. We now, therefore, proceed to the more immediate purposes of our work; taking up first that division of construction which treats of Carpentry, or the use of timber in large pieces for work more or less heavy, exterior or interior, as distinguished from the operation of Joinery, which deals with smaller pieces used generally for interior fittings, and which demand finer work and more accurate adjustment of parts. The first department of carpentry work we shall take up for consideration and illustration being that of floors, of which there are several forms or varieties. Recently what may be called " combined floors/' in which certain other materials are used along with timber, have been introduced, chiefly with a view to secure the great desideratum of a fire-proof floor. The most important of these will be noticed in their place.