NEEDLE DAMS. 



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cially where the rises are rapid, requiring much regulation, they are less adapted, owing 

 to the number of pieces to be handled and cared for, and it is probable that in 

 the United States their use will be confined to the smaller streams. They have not 

 yet been developed to high lifts, since engineers have retained the view that each 

 needle should be controllable by one man, but the example of the Louisa dam has 

 shown that this is not a desideratum, and other examples are now under construction 

 in which the size of needles and depth of water will be considerably increased. 



DIMENSIONS OF TRESTLES OF NEEDLE DAMS. 



DIMENSIONS OF NEEDLES. 



