94 THE IMPROVEMENT OF RIVERS. 



1899. Two pairs of gates, of 15" timbers, for a lock 36 feet wide and of 14 feet lift 



Cost of timber (39,000 feet B. M.) $690 . oo 



Cast and wrought iron , 824 . oo 



$1514.00 



Framing, placing, and miscellaneous 1406 .00 



(about $48.50 per M.) 



Total $2920 .00 



About $101 per M., or $1.45 per square foot. 

 (No valves in gates. Cost of spars included.) 



1897. Two pairs of gates, 18" wide, of two 9" timbers, keyed, for a lock 52 feet 

 wide and of 15 $ feet lift. 



Cost of timber (5 7,600 feet B. M.) $944 . oo 



Cast and wrought iron 634 . oo 



$1578.00 



Framing, placing, and miscellaneous 2315 .00 



(about $40.25 per M.) 



Total $3893 .00 



About $67.60 per M., or $1.32 per square foot. 

 (These had no valves in the gates. Cost of spars included.) 



The cost of wooden gates on the North German canals, for heights of 30 feet and 

 widths of chamber of 42 feet, is stated to be about $3.60 per square foot, and for double- 

 sheathed iron gates of the same size about $4.50 per square foot, or one-fifth more. 



The cost of wooden gates at certain French harbor locks is given as $5.50 to $7.00 

 per square foot for widths of chamber of 42 feet to 52 feet, and the cost of iron gates 

 for widths of chamber of 69 feet as $8.20 per square foot. 



On the Manchester Ship Canal, with a depth of water of 40 feet and a width of 

 chamber of 65 feet, the cost of greenheart gates was about $41,000 per pair, the estimate 

 for iron gates of the same size having been about $28,000 per pair, or one-third less. 

 Greenheart timber was used in preference to iron on account of its superior durability.* 



The cost of several sets of steel gates, erected between 1898 and 1902 on certain 

 tributaries of the Ohio River, ranged from $2.70 to $3.20 per square foot in place, the 

 heights being from 27 feet to 33 feet, and the corresponding lengths from 30 feet to 20 

 feet for each leaf. 



The contract price of the five pairs of double-sheathed arched gates for the lock of 

 the St. Mary's Falls Canal, Mich. (1893), was $182,610. The steelwork of the main 

 framing was 5.9 cents per Ib. ; the cast iron, 6.0 cents; the cast steel, g\ cents; the steel 



* Papers read before the International Congress of Navigation, Diisseldorf, 1901. 



