Chap. VIII.
BRITAIN.
503
thickness. There are two lozenges and four half lozenges cast in one piece ; that portionnext the abutment has one complete lozenge and two halves. The lower parts of the
Fig. 502.
FOUNDATION COURSES,
lozenges are connected together by an arch on the extrados of the voussoirs, and the upperportions are united in a similar manner ; the entire space between the road and the vous-soirs is divided into four distinct series of triangles. That part of the ribs upon which thefirst series rests has a number of grooves made in the extrados of the voussoirs to receivethem, and they are secured by iron bolts passing through the bases and the voussoirs.
Weight of the Materials of Half the Middle Arch.
Voussoirs.
Diagonals.
Transverse.
St. Andrew’sCross.
Lozenges.
Total.
Tons
Cwts.
Tons
Cwts.
Tons
Cwts.
Tuns
Cwts.
Tons
Cwts.
Tons
Cwts.
Xo. 1
62
18
6
11
11
0
9
10
26
4
112
3
2
60
9
2
12
10
13
8
15
20
3
102
12
3
54
15
2
13
10
2
8
2
32
16
108
8
4
51
3
2
]
9
17
-
24
5
87
16
5
50
17
2
18
9
15
-
32
14
95
19
6
51
2
2
13
9
15
-
-
24
15
88
5
7
25
12
2
12
-
-
-
-
20
7
48
11
643
14
Tons Cwts.
Plates that cover the bridge under the road
-
-
152
0
Cornices and railing -
-
-
77
3
Road and pavement -
-
-
650
0
Plates resting on the piers and abutments -
-
-
13
0
Total weight of iron in the three arches
-
-
- 5,584
0
Weight of a half pier -
-
-
- 11,000
0
The price of casting, transport, and fixing, was 18/. per ton.
Of Mr. Telford’s iron bridges, that over the river Spey at Craig-Ellachie consistsof one arch of 150 feet span, with a rise of 20 feet. Subsidiary to this main arch, but atsome distance from it, are three others, built of stone, 15 feet span each, under the easternend of approach ; the total water-way is 195 feet. This bridge is beautifully situated about12 miles above Fochabers, where the Spey, rushing among lofty rocks, has cut a deeppassage for its waters, and the slender arch, amidst the birch trees and native firs, rendersthis spot truly interesting; the total cost of the bridge and its approaches, including therock-blasting on the east side of the river, was not more than 8200/.
k k 4