148 



THE IMPROVEMENT OF RIVERS. 



feet apart, are bracc<l by channel-irons placed on each side of the rods suspending the 

 frames. The brackets are trajK-zoidal in form and 2 feet high. Upon each of their 

 faces two angle-irons are riveted, projecting on each side and forming a guide. The 

 heads at the end* of the sus] ending bars rest upon these guides, 1.64 feet under the 

 cross girders, so that the uprights can be raised to the llanges. 



The width of the up-stream roadway de]x.-nds on its height alxivc the water. There 

 must be space enough, from the md girder to the point where the chain comes through, 

 to work the windlass; also to give the chain a proper inclination, to avoid too much 

 tension on it. At Poses the chain is attached to the frame at 2.95 feet below the water- 



GENERAL SECTION OF POSES DAM. 



level, and the chain is inclined 33 at the beginning. The distance between the prin- 

 cipal girders of the up-stream roadway is 24.76 feet for the navigable passes, and 17.22 

 feet for the non-navigable passes. 



The up-stream roadway is placed half-way up the principal girder, so as to allow 

 sufficient space below the cross girders to store the rolled curtain when the frames are raised. 



The frames, which support the curtains, are wrought-iron girders, inclined so 

 that the vertical passing through the center of gravity of the frame with its curtain 

 and foot-bridge is on the up-stream side of its upper joint. They have an I-shaped 

 section, which is constant in width for 8.20 feet above the upper pool for the same pass; 

 this width is 1.64, 1.96, and 2.30 feet for the three passes, respectively. Above this level 

 the width tapers to 0.82 foot at the top. 



The joint with the suspender bars is made by a cast-steel eye riveted to the web 



