432 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[November, 



Figure 2, shewing the lower tier of Braces and part of Lock. 





Speci^cation of the coffer dam for (he entrance loch; to he 1^1 feet long, 

 and its form as reprtstnttd in the drawings. 



The principal dam to be made of two rows of piles at a distance of 

 6 feet apart, of Memel or Dantzic timber 12 inches square, also an 

 outer row of piles of the same timber 12 inches square at 8i feet from 

 the main dam. An inner row to be driven to strengthen the foot of the 

 main dam at 5 feet from it, of tir timber 12 inches square, the piles to 

 be driven 8 feet below the lowest part of the lock. All the piles to 

 be perfectly straight and parallel on two sides, and shod with wrought 

 iron shoes not less than 15 lbs. each, strong iron hoops also to the 

 heads, the iron 4 inches broad by 1 inch; the guage piles to be driven 

 opposite each other, at the distance of 10 feet apart, and their heads 

 when driven to be 4 feet above high water-mark of an 18 feet tide ; 

 when they are driven to the proper depth, two rows of temporary 

 double walings 12 inches by 6 inches to be bolted to them, the upper 

 one to be one foot above high water-mark, and the other as low as the 

 tide will admit, allowing a space of not less than 12 inches wide be- 

 tween the wale piece?, for the piles to till up the bays between the 

 guage piles, the bolts to be H inch square iron, 3 feet long in the 

 clear, and to pass tlirough the walings and the piles, and also two 

 pieces of timber (J inches thick to be placed under the head and nut 

 of each bolt ; the remainder of the piles to fill up the bays are to be 



driven, and each bay keyed in with wedge piles to make the dam water 

 tight. When all the piles are driven, the temporary walings to be 

 taken oft, the jonits between the piles of the outer row of the main 

 dam to be caulked where necessary with tarred oakum, 3 rows of 

 permanent single walings are then to be put on, as shewn on the draw- 

 ings, ol timber 12 inches by 6 inches, and in lengths not less than 20 

 feet, the two rows of piles to be tied together with screwed bolts and 

 nuts with plates, to pass through the walings and piles, and also the two 

 pieces of timber, the bolts to be of the best scrap iron 2 inches dia- 

 meter and proper lengths, the distance between each bolt at the 

 bottom tier is not to exceed 5 feet, and the middle tier 7 feet, and 

 the top 10 feet. The dam is then to be tilled with good clay to the 

 level of 3 feet above the bottom tier of the bolts, and from thence to 

 3 feet above high water of a spring tide, with bricks laid in sand.* 

 The guage piles lor the outer rows to be driven 10 feet apart, and the 

 heads when driven to be G feet above low water-mark of spring tide, 

 two rows of temporary w alings 12 by 6 to be bolted to the guage piles 



(here appears licre to be some discrepancy botween the specification and 

 tlio drauings, tlie latter shuw the dam to be filled in widi claj up to the 

 level ol high water-mark, vhich we imagine was the way it waseiecuted, 

 then the bricks were laid in sand to the height of 3 feet above the clay. — 

 Editor. 



