Chap. VI.

FRANCE.

283

economy in its application, and some of their first iron bridges over the Seine gave way,or were afterwards remodelled or removed.

Fig. 293. DRIDGB OF THE LOUVRE.

Fig. 294.

BRIDGE OP THE LOUVRE.

Poyet, an architect of considerable eminence, who gave the design for the beautifulfaijade of the Chamber of Deputies, turned his attention to constructions of iron, andlaboured much for its general introduction.

This foot-bridge has been greatly admired for its lightness; but, as constructed in thefirst instance, its strength was not found sufficient, and some upright supports w'ere added;the alterations made are shown by the additional strength given to the ribs and platformabove; and also by the diagonal braces of iron introduced in the outer divisions.

Pont du Jardin du Roi> at Paris , commenced in the year 1800, and finished six years after-wards, was designed by M. Lamande. It has five arches, resting on stone piers, 9 feet10 inches in width, and 21 feet in height, above the level of the water. The arches areparts of circles, the chord of which is 105 feet, and the versed sine 10 feet. There areseven ribs at the distance of 7 feet apart, formed of a series of voussoirs, 4 feet 9 incheslong, attached to each other by a number of wrought iron bolts.

The spandrils are filled with other frame-work, composed also of portions of circles,united by radiating and upright piers of iron : the principals are connected with rods ofcast-iron. The timber frame, or platform, which covers this bridge is gravelled, and thefootways are paved with stone.

After its construction, it was perceived that several of its parts near the abutments hadyielded, and a considerable fracture was the consequence: this gave rise to many inquiriesinto the properties of the metal employed, and since that period other iron bridges havebeen constructed : but there is no treatise on the subject by the French engineers. Wherestone abounds of such excellent quality, there seems to be no inclination to substitute ironfor its use: and as that metal is not obtained at a very reasonable rate, it is not probablethat it will be employed so generally as in England.

The iron bridges in which the principles of timber construction have been preferred tothe introduction of the voussoirs, or the practice of the mason, are decidedly superiorin effect: the experiments of Mr. Telford to form a suspended centre for his intendedMenai Bridge gave rise to much of the constructions employed upon iron bridges in