

PROTECTION OF BANKS. 71 



Construction. The revetments of the Mississippi River below Cairo are usually 

 constructed as follows : The bank is first cleared for a distance of 50 feet back from the 

 top and is then graded on a slope of 4 to i, measuring from the low-water line, by 

 hydraulic processes. This is followed by a dressing of the new slopes which includes 

 the filling of holes and the removal of snags, stumps, etc. A cluster of piles is then 

 driven near the upper end of the space to be covered and at zero line, and below this 

 cluster, or abutment as it is called, single piles are driven at intervals of 100 feet for 

 the full length of the mattress, in order to keep it over the zero line, during a limited 

 fluctuation of the water surface, while being built and sunk into position. The mat- 

 tress is built on barges placed end to end and near the shore, up-stream of this abutment 

 and row of piles. These barges lie outside of others, called mooring barges, which are 

 tied to the shore by wire lines. The method of construction in detail as shown by a 

 Government report* is as follows: Hardwood poles, as large as can be conveniently 

 handled by a gang of men and reasonably straight, are laid in two lines on ways over 

 and parallel to the inner gunwale. These poles lap each other 10 to 15 feet, the 

 two lines breaking joints. Where they lap they are spiked together, and they are also 

 tied together with No. 12 galvanized wire at intervals of 10 feet. Two ties are made 

 at the laps. This line of poles is as long as the mattress is wide. About 7 feet 6 

 inches apart on these poles and at right angles to them the butt ends of weaving- 

 poles made of live willow or cottonwood brush from 4 to 6 inches in diameter and 

 25 to 30 feet long are fastened with spikes and wire. Another set of poles similar and 

 parallel to the first are placed on these and securely spiked and wired. To facilitate 

 weaving, the tops and the bottoms of the weaving-poles are shaved and the knots 

 trimmed. A cable made of eight strands of No. 12 wire is fastened around the head 

 of the mat at every third weaving-pole and run up alongside of it, the end being 

 fastened thereto by two staples. These cables are 24 feet long, with an eye in one 

 end, to which, after each shift of the mat, a new length is looped in weaving. Ten 

 continuous cables are thus formed in the mat, greatly strengthening it longitudinally. 

 When this head is finished, lines are connected to it from the shore, passing under 

 the mooring barges. 



The brush used for weaving is live straight willow of any length over 25 feet and 

 from 2 to 4 inches thick at the butt. 



The butts are placed over one weaving-pole and project 2 feet beyond, being woven 

 at the other end over the next pole, under the third, over the fourth, and so on, the 

 light ends being always left on top. A strip 5 feet wide is thus woven. In the next 

 strip the butts are reversed, the butts changing .directions every 5 feet. When the 

 mattress is woven within 2 feet of the end of the poles, giving about 22 feet length of 

 mattress, it is swung in position with the accompanying barges. The head-lines on the 

 barges and mattress are slackened until the barges are nearly normal to the shore, 

 with their inside edge resting against the pile abutment. The slack in the mooring 



* Report of the Chief of Engineers, U. S. Army, 1891, p. 3606. 



