232
HISTORY OF ENGINEERING.
Book I.
of the last cone to the Fort De Querqueville, 7685 feet, making the total width of theharbour 23,424 feet.
After the cones were placed, they were loaded with stone, and a great quantity werethrown in around their bases, and between their several intervals for the purpose of breakingthe force of the sea: by the 1st of October, 1795, there had been deposited upwards of100,000,000 cube feet of stone ; or, as Cessart has given it, 381,789 toises, 4 feet, 7 inchescube.
Each of these conical cases contained as follows: —29,040 cube feet of oak, and 8705feet of beech, an allowance of 7549 cube feet being made for waste, so that there appears tohave been used for the construction of one entire cone 45,294 cube feet of timber, whichwas delivered at the price of about one shilling and ten pence per foot cube.
The total cost including labour, iron work, cordage, and the other materials required,amounted to about 8418 pounds sterling, or about double the first cost of the timber.
Cessart has given a full and detailed account of the cost of the barrels, vessels, buildingsheds, tackle employed, as well as ropes, and all other matters, from the commencement onApril 1, 1783, to January I, 1791.
The timber and iron work of the eighteen cones - :£102,600
Workmanship and the immersion of the eighteen - 65,024
Stones thrown into the cones, and to form the dyke - 620,004
Buildings and various other expences .... 98,312
Expences for superintendence, &e. - ... - 16,500
Making a total of - - - - - - 902,440
expended upon this breakwater.
The timber of the cones, in consequence of neglect and the work not having been finished,soon went to decay, and the stones they contained fell into a natural slope with those aroundthem. From the statement made by Cessart, it appears that those placed near togetherlasted three or four years, and almost all the others were entirely destroyed the year of theirimmersion, as he had foretold.
The National Assembly in the year 1791 commissioned Cessart to prepare plans for thecompletion of the breakwater, when he suggested that the dyke which then existed shouldbe covered with large masses of stone. The talus or slope towards the bay was found tohave remained at an angle of 45 degrees, while on the other side, having been formedon too rapid an inclination, it had been destroyed to within 14 feet below low water, andthe stone rolling out to sea had produced a talus of one in ten. He then laid down a plan forconstructing a breakwater by throwing in a further quantity of stone, and covering all thoseparts which appeared above low water with blocks of granite, as large as could be ob-tained ; this, however, was not executed, although in the year 1804 a number of large blockswere raised in the centre, and a battery formed upon them.
Havre de Grace is a sea-port strongly fortified, and situated at the mouth of the Seine ,on its northern bank; it is in 49° 29' north latitude, and 0° 6' east longitude. Theharbour contains three basins, within the walls of the town, calculated to receive 450vessels.
On Cape de la Heve , which is two and a half miles from the harbour, on the northernextremity of the Seine , and nearly 400 feet above ihe level of the sea, are two lighthouses,each 50 feet in height, about 325 feet apart. At the mouth of the harbour is a round tower,constructed by Francois I. , in 1509, over the door of which was his equestrian statue; itwas the intention of the monarch to have made Havre one of his principal ports, and tohave given it the name of Fram^ois de Grace ; he fortified the harbour, which then containedfifty large vessels, sixty smaller, and twenty-five galleys. This fleet was prepared tooppose Henry VIII. in his attacks upon Boulogne.
Henry II . made some improvements, and it was decided that the direction of the entrance,which was south-west, was too much exposed to the south-east and north-east winds; butno alteration was then made.
De Cessart prepared a design, which was not carried out, for three basins which wouldhave contained 300 vessels, and the outer port 250 vessels. Honfleur , with its two basins,contains sixty.
The lock gates which communicate with the basin are 40 feet in width ; and getting outof repair, De Cessart was employed to put in a new platform, and restore the injuries pro-duced by time.
After having secured the new planking to the old platform by means of iron bolts, helaid down new sills 44 feet in length, which entered the masonry of the side walls at oneend, and were secured by iron screw bolts at the other. After the grillage was complete,and thoroughly pinned down to the old work, the intervals were filled in with brick, laidin cement.