494 



FORESTRY AND IRRIGATION. 



December, 



about one-tenth of 

 whom were skilled Ital- 

 ian masons. 



The sluices are ar- 

 ranged in tiers at three 

 levels. Iron gates of 

 the Stoney system, run- 

 ning on rollers in steel 

 grooves, permit the 

 closing or opening of 

 all the sluices in a very 

 few moments, the gates 

 being suspended o n 

 steel wire cable and 

 falling by their own 

 weight. The winches 

 are operated by hand. 

 A few^ of the sluices are 

 lined with iron, but the 

 greater number are 

 lined with dressed gran- 

 ite blocks of large size. 



Around the western 

 end of the dam a ship 

 canal 32 feet wide, with 

 four locks, has been 

 completed. This canal 

 added very materially 

 to the total cost of the 

 dam. The gates in the 

 canal are said to be 

 constructed on plans 

 drawn for lock gates 

 on the proposed Nica- 

 raguan canal. 



The sluice gates in 

 the dam are opened 

 during the first part of 

 the flood season. In 

 this time the muddiest 

 part of the flood passes 

 through the dam. As 

 the river commences to 

 fall -and fortunately 

 the water carries much less sediment at 

 that time the gates are gradually' low- 

 ered. As the flood subsides a portion of 

 the water is thus held up, and when the 

 season of low water arrives, with its 

 consequent scarcity in the perennial 

 canals lower down the river, the reser- 

 voir is full. Then the gates are slowh' 

 opened, and as the river continues to 



LOCK GATE ON THE SHIP CANAL AROUND THE DAM, BUILT FROM 

 DESIGNS M.ADE FOR THE NICARAUGUAN CANAL. 



of the dam is arranged so that the res- 

 ervoir will be empty and the gates of 

 the sluices open when the flood again 

 comes down the river. There are no 

 canals of large size taken from the river 

 near the dam, so the water which is 

 stored is turned into the river and taken 

 out again further down the stream. 

 By this system of managing the gates 

 fall the reservoir supply is drawn upon in the sluices it is hoped to allow the 

 and the flow down-stream from the dam greater part of the muddy water to go 

 maintained sufficiently to irrigate the below the dam and to store the clearer 

 desired acreage of land. 



The flow out waters of the later part of the flood. 



