1887,] : 33 [ Haupt. 
THe Jerry System As at Present APPLIED. 
In applying tidal scour to the improvement of harbor en- 
trances in the United States, these three (3) principles have 
been laid down as fundamental : 
1. The works should be so designed that “they should not im- 
‘pede the inflow to such an extent as to prevent the tidal 
“basin being filled at every influx of the tidal wave.” 
2.“ They should control the outflow to such a degree and in 
“such a manner that a channel of the required depth will 
“be maintained through the bar.” 
3. “They should not to any considerable eaxtent, cause a move- 
“ment seaward of the main body of the bar; that ts, the 
“general position of the bar should be independent of the 
“effects produced between and beyond the heads of the 
“ jetties.” 
The attempt to reconcile these conflicting conditions as to 
concentration of ebb and free admission of flood resulted, after 
mature consideration, in a plan involving low or submerged 
jetties, which were tried as an experiment both at Charleston 
and Galveston. The result has been to push the body of the 
bar seaward, without at the same time materially deepening 
the water on its crest. The cost of these experiments has 
reached nearly $3,000,000. 
These plans are defective, not only in their failure to depress 
the plane of tidal scour over the bar, but they are so designed 
as to divert the ebb stream directly into the face of the flood, 
Where the resistance to be overcome is the greatest. The plans 
for Galveston have been modified, and it is now proposed to 
raise the jetties to high water, at an estimated cost at this port 
alone of $7,000,000. But even if this be done upon the two 
PROC. AMER. PHILOS. SOC, XXV. 127. E. PRINTED FEB. 21, 1888. 
