MEANS OF COMMUNICATION. 41 
was burned by the French in the campaign of 1799. It consisted of two 
spans of 171 and 193 feet, resting upon an old stone pier which belonged 
to a former stone bridge upon the same site, and which had been swept 
away. ig. 1 is aside view with one half of the covering removed; jig. 2 
a plan of the road timbers; jig. 3 a plan of the roof; jig. 4 a cross-section ; 
jig. 5 a view of one of the hollow suspension frames ; jg. 6 a section of the 
roof ; fig. T a portion of the notched girders ; fig. 8 a perspective view of the 
joints used for uniting the separate pieces of the above. rom these figures 
the construction of the bridge and the arrangement of the timbers are appa- 
rent. Originally it was intended that the bridge should stand without the 
pier; this was suffered to remain, however, and some years later Gruben- 
mann, fearing that it might also be carried away, added the braces, b, 7, seen 
in jig. 1, for the purpose of making the bridge independent of its central 
support. | 
A bridge over the Limmat, near the Abbey of Wittengen, was also erected 
by the same carpenter, assisted by his brother John Grubenmann, and burnt 
soon after that of Schaffhausen ; it consisted of one opening of 390 feet span, 
with a rise of 43 feet, and was a more solid and even asuperior piece of car- 
pentry to that at Schaffhausen. This was the greatest span ever executed 
with timber. Its radius of curvature or curve of equilibrium was about 
600 feet. 
Fig. 9 shows an arch of peculiar construction of the viaduct over the 
valley of the Ouse, on the North Shields and Newcastle railroad ; jig. 10 is a 
cross-section of the same; jig. 11 a view from above of one of the piers, 
showing the arch upon one side and the road timbers upon the other ; jig. 12 
is a side view of a portion of the pier a, with the foot of thearch B; fig. 13a 
vertical section showing the manner of uniting the planks ; jig. 14 is a cross- 
section showing the connexion between the arch and the braces; jig. 15 is 
a front view of a pier A, with the cast-iron shoe in which the arches B rest ; 
jig. 16 is a view of the said shoe, c; jig. 17a@ longitudinal section of the 
same; jig. 18 transverse section of the same, with the clamps which secure 
it to the pier A; jig. 19 is a section of the top of a pier, showing the road 
timbers and railing ; jig. 20 shows the manner of bolting the ribs beneath 
the roadway F and & to the crown of the arch; jig. 21 shows the connexion 
of the roadway u with the railing p at a point immediately over the crown 
of the arch B, over which the timbers © and F meet; jig. 22, cross-section 
of this joining on a larger scale ; fig. 23, side view of the same; jig. 24, sec- 
tion of joinings of these timbers; jig. 25, the joint between the timbers Fr 
and = and the cross-ribs ; jig. 26, joint between the rib a and the flooring ; 
jig. 27, detail of the connexion between the timbers © and the pier a, and 
by means of the cross-ribs t with the arch 3, also through the carriers o 
with the longitudinal timbers of the roadway ; jig. 28, section of the foun- 
dation piles, with the platform and grillage. 
Another bridge with a notched timbered arch deserves to be mentioned 
in this place. This is a bridge over the Schuylkill at Philadelphia, covering 
an opening from one abutment to the other of 340 feet 32 inches. 2. 8, 
Jig. 29, is a view of the bridge, with the covering removed from the left half 
621 
