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HISTORY OF ENGINEERING.

Book I.

having no solid connection with their neighbours, the impression goes no farther, but thetremulous motion raised in one part of a boarded wlmrfing is communicated over a largearea, which in time loosens the earth behind, and, as the tides enter by degrees, bringsthe whole to ruin.

“ Wherever the foreshores are not broad enough, from low water to neap tide high watermark, to stand by a natural slope, they should be reduced to a slope of two to one, that isto batter two feet to one perpendicular ; and this being covered a foot thick with rubblestones of all sizes, bedded together and footed upon the rubble, thrown in to support theground under low water mark, will make a lasting and durable defence, and will resist anyordinary force, but, if exposed to the waves of the open sea, the cover must be increased inweight and thickness. This method will answer if the batter is three to five, or even oneto one, but the first inclination is preferable.

“ Banks , to be secure against inundations, must not only be high enough, but sufficientlystrong, and experience here is the best guide. They are proof only when they stand atleast a foot higher than the level the waters are known to rise. It is not, however,necessary to preserve the same slope above the high water mark of equinoctial spring tidesto the extremest height as below that mark, because they will seldom come to such astress, yet they ought to be sufficient to answer if they are put to it.

“ In order to do this, they should be at least 3 feet broad at the extreme height, and threetimes as much broader at the level of the equinoctial spring tide mark, as the extremeheight exceeds their height.

“ The artificial banks below that mark should be at least four times as much broader intheir base or seat, upon the natural level of the ground, as the perpendicular height of thesaid extreme tide mark is above the natural level of the ground, whereon each part of thesaid bank stands: when the earth is loose, sandy, or moorish, the bases or seats and topsshould be respectively broader.”

The harbour has undergone considerable improvement at various times, since Mr.Smeaton was called upon to make his report, but the anchorage is not good, in conse-quence of the oozy bed of the river, which has several times changed its direction. TheGreat Ouse now carries its water by a new cut from Littleport Chain to Uebeck, and theLittle Ouse is a narrow stream.

There can be no doubt that the harbour has sustained considerable damage from theobstructions, which prevented the ascent of the tides tip the river ; it is not a quarter of amile in breadth at Lynn, though six miles below its width is four times as much; onsome occasions the tide flows in so rapidly, that it has received the name of the Bore, andits violence frequently changes the curvature of the channel.

This town, distant ten miles from the coast, enjoys considerable commercial advantages,and by means of the Ouse and its tributary rivers communicates its navigation with eightcounties ; its inhabitants have received from various sovereigns as many as fifteen charters;four small rivers, called fleets, divide the town, which is surrounded by a deep ditch,flanked by a strong wall which originally was strengthened by nine bastions.

JFisbeach, the most northern town in Cambridgeshire , derives its name from its situationon the banks of the Ouse, or )fls, which flows through it into the sea, about 8 milesdistance. All the waters, which were directed by a channel, cut in the reign of Edward I. to benefit Lynn, once passed through this place; the town, however, from its situation,carries on considerable trade.

Boston , situated on the Witham, about 5 miles from its mouth, is an important port ofthe gulf called the "Wash ; some few years ago the channel of the river was considerablydeepened, and an iron bridge of a single arch, 86 feet span, designed by Mr. Rennie, wasthrown across it; the width of the carriage way was 39 feet, and the abutments are so keptdown, that there is not much rise from the horizontal direction.

The tower of the church, somewhat resembling that of the cathedral at Antwerp , 282feet in height, has a lantern at top, which formerly served as a guide to the navigators ofthe Boston deeps.

The whole of the country around Boston is subject to inundations; in 1820, a highspring tide, accompanied by a violent tempest, broke through the sea embankment, and didconsiderable damage.

Grimsby , formerly the emporium resorted to by merchants from Norway and thewestern islands, had its commerce destroyed by the silting up of its famous harbour: this,however, has been partly improved, and a dry dock, constructed at a vast expense, hasrestored some of its former prosperity.

Bartnn-upon-Humber , about three quarters of a mile from its banks, carries on considerabletrade, from its position on the Ancholme canal and the basin of the Humber.

Port of Goole , Yorkshire , is on the Ouse, at some distance from where it falls into theHumber , and near to where the Dutch river forms a junction with the former; this port,therefore, is considerably more inland than Hull, and has two wet docks and a basin. The