Stone platforms, or half or quarter spaces, of geome trical stairs, consist of one or more stones, as they can be procured ; when two or more arc used, the first stone should be laid upon the upper step, with its edge wedg ed into the wall ; the next stone must be joggled or re bated into the one just set, and its end also fixed in the wall. The same mode must be pursued w ith the remain ing stones, till the platform is completed. In cases where a second flight of stairs is required, the last stone of the platform becomes an abutment for the lower step of the next flight, and the joints must be joggled as in the for mer flight.
Geometrical stairs, constructed of stone, depend upon the following pi inciplc : that every body must be sup ported by three points at least, placed out of a straight line ; and consequently, if two edges of a body, in dif ferent directions, be secured, they eN ill become relatively immoN cable ; such is the case in a geometrical stair ; one end of the step is always tailed into the wall, and one edge rests either on the ground or on the edge of the in ferior step or platform.
The practice of wooden stairs, (which also includes the constructing and fixing the handrails for those of stone,) falls under the article Jo ER V, to which we must refer. But besides the before mentioned materials, stairs may be constructed with cast iron, which would, in the case of fire, have advantages over either of the former. The facility with w hich the several parts may be case and fixed, and the light and elegant forms which may be introduced, at a comparatively moderate expense, lead us to press this new mode upon the attention of the young architect.
The staircase 1.-es always been considered a principal feature, not only in the private dwelling, but also in the public edifice. It is usually placed so as to be seen from the hall or vestibule, and centrical for communicating with the public or principal apartments ; it is frequently decorated with columns and pilasters on the sundry land ings; it is generally terminated at the top by an elegant skylight window, and has its walls enriched with pannels for paintings, and niches for statues or busts.