agriculture has been busy with its plastic hand. Such a scene as this is peculiarly characteristic of the Island, in its present state of peace and prosperity; and, when contrasted with the appearance of the country but a few centuries back, singularly displays the hand of a benignant Providence, urging forward and directing the labors of industrious man.

ELEVENTH WEEK-THURSDAY.

ARCHITECTURE.—ITS

MODERN HISTORY AND PRACTICE

BRIDGES.

THE invention of the arch, besides making a most essential difference in the art of house-building, gave peculiar facility to another important improvement, which the intercourse of society required, the means of conveyance across rivers and deep ravines. The Romans, to whom we have traced the first free use of the arch for the former of these purposes, seem to have been also among the first who applied it in the construction of the latter. Of these ancient works, one of the most remarkable which still remains, and, indeed, of which we have any account, is the bridge of Alcantara, in Spain. It is constructed over the Tagus, and consists of six arches, of about a hundred and twelve Spanish feet each, the height, from the bottom of the river to the road-way, being two hundred and five feet.

At the close of the dark ages, the revival of bridgebuilding in Europe was greatly aided by the enthusiasm and reveries of a poor shepherd, in the neighborhood of Avignon, in France. A religious fraternity had previously been formed, under the title of Brothers of the Bridge,' whose duty it was to facilitate, by every means, the passage of rivers. The person of whom we speak, did not originally belong to that brotherhood; but, while following his duties as a shepherd boy, before he was twelve years of age, is said to have received repeated

revelations, commanding him to quit his flock, and undertake the building of a bridge at Avignon. Whatever might be the nature of the impulse he received, the enthusiastic youth obeyed it, and arrived at Avignon just at the time when the bishop was preaching, to fortify the superstitious minds of the people against an eclipse of the sun, which was to happen the same day. In the church, the young adventurer raised his voice, proclaiming that he was come commissioned to build a bridge over the Rhone. The proposal, falling in with the views and wants of the people, was received with applause; and, notwithstanding the contemptuous opposition of the magistrates and men in power, was carried into effect by the contributions of the inhabitants and the zeal of the clergy, aided by the performance of many pretended miracles. This bridge, which was composed of eighteen arches, was begun in 1176, and completed in 1188. Part of it has resisted the ravages of time and the destruction of war, and remains, to this day, a monument of religious fanaticism, applied to a most useful purpose, and developing scientific skill. The extraordinary individual who animated and superintended the work, was afterwards known in the Romish calendar by the name of Saint Benezet. In the year 1454, a bridge was built in the same country, at Vielle-Brionde, over the river Allie, the span of which was a hundred and eighty-three English feet, the greatest effort of architectural skill that has yet been exemplified in an arch of stone. At Schaffhausen, however, in Switzerland, a wooden bridge was erected in 1758, the length of which was no less than three hundred and sixty-four feet, without any support but that of the abutments on the banks of the river; and what added to the wonder was, that, for some reason which is not mentioned, if not accidentally, the bridge was made to bend eight feet out of the straight line.

In Britain, a new era has, in our own age, been introduced into the art of bridge-building, by the use of iron. The first cast-iron bridge was erected over the river Severn, near Coalbrook Dale, in 1777, the span of which is upwards of a hundred feet. Subsequently, another, of a

hundred and thirty feet span, was thrown over the same river; and, in 1796, a bridge of similar materials was built across the river Wear, at Sunderland, the extent of which was two hundred and thirty-six feet.

The bold and rapid progress of this new species of bridge-building, indicated a power that was not destined to be confined within such narrow limits. Mr. Telford* gave in a plan to a committee of the House of Commons, for rebuilding London Bridge, by which he proposed to throw a bridge of one arch across the Thames, the span of which was to be six hundred feet, and the versed sine, or height of the arch, sixty-five feet. This plan met the approbation of the Committee, and was by them submitted to the investigation of twenty persons, most eminent in Britain for scientific knowledge or practical skill. Their reports justified its adoption, but a rapid succession of political events interfered with its execution.

The most remarkable exertion of skill in bridge-building, however, which has actually been reduced to practice, is that of the magnificent iron-bridge over the Menai, of which Mr. Telford was at once the projector and executor. The island of Anglesey is divided from Caernarvonshire, by the celebrated strait, or arm of the sea, named the Menai, through which the tide flows with great rapidity, and, from local circumstances, in a very peculiar manner. This rendered the ferry difficult and hazardous, and it had long been a matter of speculation, how this important line of communication with Ireland, by the port of Holyhead, could be improved. Wooden bridges, and embankments with draw-bridges, had been alternately proposed and abandoned. Mr. Rennie, the celebrated civil engineer, had given in a report to the House of Commons, in 1810, in which he projected two plans, one to pass over the Swilley Rocks, by a castiron bridge of three arches, each of three hundred and fifty feet in span; and the other to unite the mainland with the island, at the narrowest point, by a single arch,

* Mr. Telford was a native of Dumfriesshire, who, by his genius, raised himself from the station of a common mason, to that of one of the most celebrated engineers of the age.

of a span of four hundred and fifty feet. The latter plan, however, he declared to be, if not impracticable, at least "too hazardous to be recommended," because of the difficulty and risk in constructing a centre of such vast extent, "without any convenient means of supporting it in the middle, on account of the depth of water, and rapidity of the tide." But Mr. Telford, having been afterwards employed, had sufficient ingenuity to obviate this difficulty, in the adoption of a new mode of centering by suspension, instead of support from below. This plan was carried into successful execution, and has introduced a principle of the utmost utility, the limits of which it is not easy to estimate. By constructing a bridge on this principle, of five hundred feet span, and raising it in the centre to the height of a hundred feet above the surface of the tide at high water, he has accomplished a work, which, while it completely answers the purpose of road communication, leaves the navigation unimpeded, giving free passage to vessels of a hundred and fifty tons burden, with all on end," and of three hundred tons burden, with their top-gallant-masts struck.

Into the details of this remarkable work I shall not be expected to enter; but the principle may be stated in a few words. The power of suspension is obtained by raising, at each abutment, buildings of masonry, to an adequate height, over which iron chains are made to pass, which are secured on the land side by being inserted into the solid rock. The mode of constructing the centre, or frame-work, was the principal achievement in this bold and ingenious plan. Of this operation, Mr. Telford himself says, "it is applicable to stone as well as iron arches ;" and he adds, that the original idea "is perfectly simple, and the effects of all its operations are more capable of correct demonstration, than those of the former mode of supporting from below." The successful execution of it, on so large a scale as at Menai, has, as he anticipated, removed all difficulties with regard to carrying bridges over inaccessible ravines, or turbulent streams; and a new era has been formed in bridge-building.

The beauty of this splendid work is not less distin

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guished than its conception was sublime. It is impossible to view, without a very high degree of admiration, a fabric erected in the air by human skill, emulating the rainbow in the extent of its span, and appearing, at a dis tance, almost as delicate as the gossamer's web, while its elegant proportions, and its magnificent sweep, embody every preconceived idea of what is graceful in outline. Nor will the sentiment fail to be rendered still more intense, when it is known, that the strength and durability of the fabric are as remarkable as its appearance is airy; that a tenfold security is given to its permanence, by a combination of all the resources of science; and that difficulties, which, in any earlier period of the art, must have been considered absolutely insurmountable, have been overcome with ease and certainty. But the contemplative mind will not stop here. A principle has been successfully employed, which unfolds new and more extensive triumphs for science, in its application to schemes of practical utility; and it may be, that a few years shall not pass away, till we shall have discovered, that what has yet been executed, is but as child's play to the works which then shall be achieved. If only the activity and enterprise, which at present distinguish the age, are destined to continue uninterrupted, there is no hazard in this anticipation.

ELEVENTH WEEK-FRIDAY.

ARCHITECTURE.-ITS MODERN HISTORY AND PRACTICE

AQUEDUCTS.

ONE of the remarkable effects of commerce and manufactures is to give rise to works of art, by which easy communication may be extended, in various inland ramifications. The carriage of heavy goods, by roads, is tedious and expensive; and wherever good water con veyance can be obtained, this has many advantages. The first improvement of this kind of conveyance, has