and 39, divided by 4, gives 92; to which add half an inch, and the result will be 104 inches, the width required for the box shutter.

445.-In disposing and proportioning windows for the walls of a building, the rules of architectural taste require that they be of different heights in different stories, but of the same width. The windows of the upper stories should all range perpendicularly over those of the first, or principal, story; and they should be disposed so as to exhibit a balance of parts throughout the front of the building. To aid in this, it is always proper to place the front door in the middle of the front of the building; and, where the size of the house will admit of it, this plan should be adopted. (See the latter part of Art. 224.) The proportion that the height should bear to the width, may be, in accordance with general usage, as follows:

The height of basement windows, 13 of the width.

But, in determining the height of the windows for the several stories, it is necessary to take into consideration the height of the story in which the window is to be placed. For, in addition to the height from the floor, which is generally required to be from 28 to 30 inches, room is wanted above the head of the window for the window-trimming and the cornice of the room, besides some respectable space which there ought to be between these.

446.-Doors and windows are usually square-headed, or terminate in a horizontal line at top. These require no special directions for their trimmings. But circular-headed doors and windows are more difficult of execution, and require some attention. If the jambs of a door or window be placed at right angles to the face of the wall, the edges of the soffit, or surface of the head, would be straight, and its length be found by getting the

stretch-out of the circle, (Art. 92;) but, when the jabs are placed obliquely to the face of the wall, occasioned by the demand for light in an oblique direction, the form of the soffit will be obtained by the following article: and, when the face of the wall is circular, as in the succeeding one.

447. To find the form of the soffit for circular window heads, when the light is received in an oblique direction. Let a b c d, (Fig. 283,) be the ground-plan of a given window, and e f a, a vertical section taken at right angles to the face of the jambs. From a, through e, draw a g, at right angles to a b; obtain the stretch-out of ef a, and make e g equal to it; divide e g and e fa, each into a like number of equal parts, and drop perpendiculars from the points of division in each; from the points of intersection, 1, 2, 3, &c., in the line, a d, draw horizontal lines to meet corresponding perpendiculars from e g; then those points of intersection will give the curve line, d g, which will be the one required for the edge of the soffit. The other edge, c h, is found in the same manner.

448.-To find the form of the soffit for circular windowheads, when the face of the wall is curved. Let a b c d, (Fig. 284,) be the ground-plan of a given window, and e ƒ a, a vertical section of the head taken at right angles to the face of the jambs

Proceed as in the foregoing article to obtain the line, d g; ther that will be the curve required for the edge of the soffit; the other edge being found in the same manner.

If the given vertical section be taken in a line with the face of the wall, instead of at right angles to the face of the jambs, place it upon the line, c b, (Fig. 283;) and, having drawn ordinates at right angles to c b, transfer them to ef a; in this way, a section at right angles to the jambs can be obtained.

SECTION VL-STAIRS.

As

449. The STAIRS is that mechanical arrangement in a build. ing by which access is obtained from one story to another. Their position, form and finish, when determined with discriminating taste, add greatly to the comfort and elegance of a structure. regards their position, the first object should be to have them near the middle of the building, in order that an equally easy access may be obtained from all the rooms and passages. Next in importance is light; to obtain which they would seem to be best situated near an outer wall, in which windows might be constructed for the purpose; yet a sky-light, or opening in the roof, would not only provide light, and so secure a central position for the stairs, but may be made, also, to assist materially as an ornament to the building, and, what is of more importance, afford an opportunity for better ventilation.

450.-It would seem that the length of the raking side of the pitch-board, or the distance from the top of one riser to the top of the next, should be about the same in all cases; for, whether stairs be intended for large buildings or for small, for public or for pri vate, the accommodation of men of the same stature is to be consulted in every instance. But it is evident that, with the same effort, a longer step can be taken on level than on rising ground

and that, although the tread and rise cannot be proportioned merely in accordance with the style and importance of the building, yet this may be done according to the angle at which the flight rises. If it is required to ascend gradually and easy, the length from the top of one rise to that of another, or the hypothe nuse of the pitch-board, may be long; but, if the flight is steep the length must be shorter. Upon this data the following problem is constructed.

C

Fig 285.

451. To proportion the rise and tread to one another. Make the line, a b, (Fig. 285,) equal to 24 inches; from b, erect bc, at right angles to a b, and make b c equal to 12 inches; join a and c, and the triangle, a b c, will form a scale upon which to graduate the sides of the pitch-board. For example, suppose a very easy stairs is required, and the tread is fixed at 14 inches. Place it from b to f, and from f, draw f g, at right angles to a b; then the length of ƒ g will be found to be 5 inches, which is a proper rise for 14 inches tread, and the angle, fb g, will show the degree of inclination at which the flight will ascend. But, in a majority of instances, the height of a story is fixed, while the length of tread, or the space that the stairs occupy on the lower floor, is optional. The height of a story being determined, the height of each rise will of course depend upon the number intc which the whole height is divided; the angle of ascent being more easy if the number be great, than if it be smaller. By dividing