BUILDING, 
the stair, nw yet in a vertical direction ; 
tlie upper sally of every step forms an in- 
terior obtuse angle, called a back rebate, 
and the lower, of course, an exterior one ; 
and the joint formed of these sallies is called 
a joggle. The upper part of the joint may 
be level from the face of the risejs, to about 
one inch within the joint. 
This is the plane of the tread of each 
step, continued one inch within the surface 
of each riser ; the lower part of the joint 
is a narrow surface, perpendicular to the 
rake of the stair, at the end next to the 
newal. In siairs constructed of most kinds 
of stone, the tliickness of every step, at 
the thinnest place of the end next to the 
newal, has no occasion to exceed two inches, 
for steps of four feet in length, that is, by 
measuring from tiie interior angle of every 
step perpendicular to the rake. 
The thickness of steps at the interior an- 
gle should be proportioned to the length of 
the step ; but allowing that the thickness of 
the steps at eacii interior angle is sufficient 
at two inclies, ihen will the thickness of the 
steps at the interior angles be half the num- 
ber of inches that the length of the steps 
has in feet ; thus, a step five feet long would 
be two inches and a half at that place. 
The stone platfjrm of geometrical stairs, 
viz. the landing half spaces, and quarter 
spaces, are constructed of one, two, or 
several stones, according to the difficulty 
of procuring them. When the platform 
consists of two or more stones, the first 
platform stone is laid upon the last step that 
is set, and ti e one end wedged in tiie wall : 
the next platform stone is joggled, or re- 
bated, into the one next set, and the end 
again fixed in the wall, as that and the pre- 
ceding steps are, and every stone in succes- 
sion, till the platform is completed. If there 
is occasion for another flight of steps, the 
la.st platform becomes a spring stone for the 
next step ; the joint is to be joggled, as 
tsell as ail the succeeding steps, in the same 
manner as the first flight. Geometrical 
stairs, executed in stone, depend on the 
following principle : that every body must 
at least be supported by three points, placed 
out of a straight line, and, consequently, 
if two edges of a body in different direc- 
tions be secured to another, the two bo- 
dies will be immoveable in respect of each 
other. This last is the case in a geometri- 
cal stair : one end of a stair stone is always 
tailed into the wall, and one edge either 
rests on the ground itself; or on the edge of 
the preceding stair stone, whether the stair 
stone be a plat or step. Tiie stones foi-nimg 
a platform are generally of tlie same thick- 
ness as those forming the steps. 
Roofs. Roof is that part of a building 
raised upon the walls, and extending over 
all the parts of the interior, wliich consists 
not only of the covering or exterior part, 
but of all the necessary supports of tliat 
part, for protecting its contents from incle- 
ment seasons. There are many forms of 
roofs, the most simple of which is that 
which has only one plane, and is called a 
shed roof ; but the form which has always 
been, and still continues to be in most ge- 
neral use, wherever the natiire of climate 
requires it to be raised, is that the vertical 
section of which consists of two sloping 
sides, is consequently triangular, and called 
a span roof. 
Here it will be proper to say something 
of the changes of inclination or pitch winch 
have prevailed in this simple form, among 
different nations, from time to time, arising 
as well from the nature of the climate as tlie 
caprice of the people, and as transmitted 
down to the present age. The ancient 
Egyptians, Babylonians, and Persians, as 
well as other eastern nations ; and also the 
present inhabitants of those climates, where 
rain seldom appears, make their roofs quite 
flat. The ancient Greeks, perceiving the 
inconvenience of this, raised them in the 
middle with a gentle inclination towards 
tlie sides ; the height from the, middle to the 
level of the walls not exceeding |th or tth 
part of the span ; as may be seen by many 
ancient temples still remaining in that coun- 
try. The Romans made the height from 
ith to fth parts of the span. After the de- 
cline of the Roman empire, high pitched 
roofs began to be in general request all 
over Europe, and the vertical section of 
that which most generally prevailed, seems 
to have been an equilateral triangle, which 
was considered as the standard. In Ger- 
many this has been remarkable, from very 
remote antiquity, as appears from Vitru- 
vius : the equilateral pitch, and that of a 
highfie one, appears to have continued as 
long as pointed architecture prevailed. 
When Grecian and Roman architecture 
was first introduced into this country from 
Italy, roofs began to be made lower, and 
the rafters were |ths of the breadth of the 
building; this was called true pitch, and 
subsequently the square seems to have 
been considered as the true pitch. In these 
