The New Orleans Democrat. (New Orleans, La.) 1875-1876, 1876-01-21
CAPTAIN EADS'
Report on the Progress or the Jetties.

OFFICE SouTH PASS JErTy WORKS,
New Orleans. In. Jan. IL. 1876.
Mr.. J. s. Walsh. President South Pass Jetty
Company St Louis. Nc:
Dear SRI have the honor to inform
you that the jetties. being constructed
under my grant from the United States,
have been so far extended into the sea
that the almost complete control Of the
river discharge has been accomplished
through n distance Of about II miles
from the lands end, and within $500
feet Of the crest OF the bar.
Up to the 25th Of December, the date
Of the last complete soundings, Mr..
Corthcll, chief assistant engineer, esti-
mated that ] 1858, 222 cubic yards had
been excavated from the bar between
the jettics. 9,
This has been nearly all accomplished
by the current since the LIST Of October,
and the larger portion OF it during the
month OF December. AS near as ] can
moving from 10000 to 10000 cubic yards
per day. A large amount Of work has
been done ut the jetties beyond this one
and half miles referred to.
Your stockholders will understand
more clearly the amount OF work ac-
complished and the amount yet to be
done, when / state that to complete the
mattress work OF the jetties up to the
low tide level, and out to point 10,5Oo
feet from the lands end, will require
only 100 additional mattresses. Mcssrs.
james Andrews IL Go. laid in position
during the last thirty days TO the 10th
Of january 1877 mattresses.
The weather is, however, so unstable
at this period Of the year that 1t may re-
quire sixty days to lay this remaining
number.
The bar crest IL now 10, 800 feet from
the lands end, and when the jetties are
extended to this point, we shall have
very complete control Of the river and
the disappearance of the crest Of the
bar will then be only question OF time,
the duration OF which we can now more
accurately estimate from the results
thus far developed.
70 secure twenty feet depth Of water
about 1900, 900 Of cubic yards will have
vet to be excavated by the current.
The lefty wor ks will extend about 1900
feet beyond the crest of the bar when
completed. A large part OF this work
is already completed, but | am con
fIdent that to secure from 20 to IS feet
of water il will not be necessary to raise
the jetties above low tide nor extend
them beyond the point named, 1O,J0
feet.
The material OF the crest Of the bar is
identically the same as that which Is be-
ing so rapidly secured out by the cur
rent from between the jetties above the
bar, and no anxiety need be INDUCED In
on account of the water not being yet
deepened on the crest of the bar.
This Is because no acceleratlOn OF the
current is created on the crest beyond
that which the water receives by the
effect of the jctties about mile above:
The first acceleration Of current will
cause the water to be charged with q
larger amount Of sediment. When thus
charged it can sustain no more, and un-
less It receives an additional accelera-
tion IL must pass over the crest OF the
bar without affecting it. But as the
channel is enlarged by this securing a
mile or SO above the crest OF the bar,
the current there gradually falls TO the
normal condition OF the river above, and
receives the acceleration further down
and nearer to the crest, and TINS lattei
result is increased by the continual ex'
tension and building up OF the Jetties
toward the crest Of the bar. Over these
unfinished parts Of the jetties some 1900
or 1000 feet long, above the crest OF the
bar. it is now flowing out literally with
an average depth Of feet, and an aver.
age depth over the crest OF the bar OF .
feet.
It will thus be seen that the enlarge.
ment Of the jettied channel first mani
tested itself at the upper end OF the
works, and that it is steadily moving
down toward the crest OF the bar.
The summit Of the bar being original
ly q plateau over half mile IN length
is now reduced to mere ridge, while
the base of the bar, estimating it at
twenty feet beneath the water surface
was originally nearly ten thousand feet
long, now it is only about sixty-two nun
dred feet long.