1490
THEORY AND PRACTICE OF ENGINEERING.
Book II.
The Bridge of Saumur , on the Loire , of which we have given some account at page 258.,was executed by De Cessart, who published a series of tables on Chezy’s principles for settingout arches, approaching the elliptical form, from 24 feet to 100 feet span: the diagramwas drawn for an arch of 60 feet opening, and by a reference to the table the distancefrom one letter to the other will be found; the radiating lines from F, N, O, G,
Fig. 2711
&c., being set off upon arcs of from 10, 20, 30, 40, 50 degrees. There are severalcalculations which accompany these tables which it is unnecessary to dilate upon: thedimensions are all in French feet and inches, which are here retained. For a consider-able time this system of setting out arches was adopted in France , and the bridges so con-structed have been very much admired.
24 Feet Opening.
A F = 20 feet 9 inches 11 lines 11| points.
ft.
in.
1.
P*
ft.
in.
1.
P-
ft.
in.
1.
P-
_ ft.
in.
1.
P-
AB =
8
4
10
E C = 7
2
4
9?
AB =12
7
3
1°3
E C = 10
9
7
n
BG =
4
0
3
n
EL = 1
t
0
9|
BG= 6
0
5
4|
EL = 1
7
7
n
GO =
i
4
9
n
LK = 0
9
7
6|
GO= 2
1
2
4§
LK= 1
2
5
u
ON =
1
10
4
9 ?
KI = 2
3
7
9\
ON= 2
9
7
2§
KI = 3
5
7
2J
NM=
2
4
0
0
IH= 3
11
0
0
NM= 3
6
0
0
IH = 5
10
6
0
MF =
2
9
7
n
HF = S
6
2
0
MF= 4
2
4
9§
HF= 8
3
3
0
AF =
20
9
11
hi
Idem. 20
9
11
i'i
A F =31
2
11
8 §
Idem. 31
2
11
I
30 Feet Opening.
A F=26 feet 0 inches 5 lines 9 points.
ft.
in.
1 .
p.
ft.
in.
1.
P-
ft.
in.
1 .
P-
ft.
in.
1.
P-
AB =
10
6
1
3
E C =
0
0
0
0
AB =
14
8
6
«*
EC =
12
7
2
4 s
BG =
5
0
4
6
E L =
1
4
4
0
BG =
7
0
6
3 i
EL =
1
10
10
4
C O =
1
9
0
0
LK =
1
0
0
3
G 0 =
2
5
4
9
LK =
1
4
9
H|
ON =
2
4
0
0
KI =
2
10
8
0
ON =
3
3
2
4 §
K I =
4
0
6
4|
nm=
2
11
0
0
I H =
4
10
9
0
NM =
4
1
0
0
I H =
6
10
3
0
IM F =
3
6
0
0
LI F =
6
10
8
6
MF =
4
10
9
n
HF =
9
7
9
6
A F =
26
0
5
9
Idem.
26
0
S
9
A F =
36
5
5
7
Idem.
36
5
5
7
36 reet Opening.
AF=31 feet 2 inches 31 lines 89 points.
42 Feet Opening.
A F=36 feet 5 inches 5 lines 7 points.