REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.


 On the top of the crest, piers eight feet in thickness, grooved for Stoney sluice gates, are to be built 38 feet from center to center, having clear openings of 30 feet. These gates, as proposed, are almost exact counterparts of the gates provided for controlling the flow from the lower end of the Chicago Drainage Canal, but the sills are to be placed 16 feet below the normal water level, instead of 15 feet, as at the Chicago Drainage Canal.
 For the whole length of the regulating works the design is the same as the centra portion, except that the concrete rests upon the surface of the rock or upon excavations made in the rock, as indicated by the two smaller sections on the plan. The water passing through the central sluices will flow directly out through the diversion channel to the Chagres; that passing through the sluices nearer the ends of the regulating works will be caught by intercepting channels sloping toward the central portion, and will follow the course indicated by the arrows on the plan, flowing toward the central portion and thence out through the diversion channel.
 The regulating works are capable of discharging 140,000 cubic feet per second when the water in the lake is not more than one foot above the normal level.
 It is thought that in connection with a great lake, such as here proposed, regulating works which can discharge a great quantity of water when the lake is at its normal level are preferable to an uncontrolled overflow spillway which will not begin to discharge water in any considerable quantity until a flood has raised the lake above its normal level.
 With the uncontrolled spillway 2,000 feet long, recommended by the Isthmian Canal Commission of 1899-1901 in connection with the Bohio dam, it was estimated that the water in the lake might be raised five feet above its normal level by a maximum flood.
 With the regulating works proposed in connection with the Gatun dam it is estimated that the surface of the lake will never be raised by a maximum flood more than two feet above the normal level, and with ordinary floods it would be feasible by beginning the discharge before the flood waters reached the lake to keep the surface from rising to any appreciable extent.
 Such sluices as are here proposed would be very objectionable on a river or even at the outlet of a small lake, but in a great lake like that to be formed by the Gatun dam the currents toward the outlet will, under ordinary conditions, be inappreciable, so that the course of any floating substances will be determined by the wind instead of by the current and they will be stranded on the shores; moreover, if, during floods, trees and other drift should be washed into the lake from the tributary rivers, they would not have time, on account of the great size of the lake, to reach the Gatun dam before the flood subsides.

 REDUCTION IN COST.

 The great quantity of material to be placed in the Gatun dam may cause it to be inferred that a structure at this place adds to the cost of the canal; but it should be borne in mind that the adoption of this site eliminates large expenditures for the canal and diversion channels between Gatun and Bohio. A comparison shows that there is a saving of $11,894,621 in the estimated cost of works by the change in the location of the dam, made up as follows:

 Works omitted.
Bohio dam --- ....------- -------------------------------------------------------------------- $6, 369,640
Gigante spillway -- ...------------------------------------------------------------------------- 1, 2Ci, 419
Canal between Gatun and Bohio--...------------------------------------------------------------- 7,643,067
Pefla Blanca outlet----------- .-- .----------------------------------------------------------- 2,448,076
Chagres diversion---------.... ----------------------------------------------------------------- 1, 929, 982
Gatun diversion .......----------------------------------------------------------------------------100, 000
 19, 700, 184
Add 20 per cent for contingencies, etc---------------------------------------------------------------3,940,037

 Total for works omitted..............................................................23, 640,221