New Orleans daily crescent. [volume] ([New Orleans, La.]) 1851-1866, 1852-09-06

4
The greatest depth shown by my soundings is 10 feet
and the depth of the line from the railroad ternu
| to the mouth of the Chefuncta is 16 Is feet
will certainly not be seriously urged that this deptl
Is too great at the maximum for the construction Of
work upon ping, or even upon abuments Marine works
too numerous to be here cataogued having the great
est power to resist winds and tides have been built in
water varying from twenty forty feet deep and OIL,
experience in wharf building will illustrate how easily we
make substantial work in depths of 80 and 40 feet
Where the banks not cayng those wharyes arc
fecty substantial piles driven 10 feet into ground
and the bottom penetrated is rarely the blue clay or any
| material as reliable for pilng,
The depth alone considered has nothing to deter the
engineer Impractical mechanic from attempting any work
based upon piing. We have already shown in the pre-
vous numbers sept % and 2S the bottom is prob
ably blue clay, beneath the shells and if So it is the best
kind of bottom for the reception support of piles
What then the forces and wave to be be met
and resisted by railroad constructed upon piles
Lake Pontchartrain!
wave of % feet height, will be found to have about
40 feet of width from trough trough and they succeed
each other at about interval Their yoition in this
| instance is s feet per second,
tidal wave, thirteen feet high in twohrd miles was
thrown forward at the rate eleven feet Der second
steamboat wave started at fifteen hundred feet from
shore was two minutes arriving shore The wave was
one foot high and delivered against the shore with
velocity OF 10 feet per second This was about the We
ioc Oh the boat that produced in ascending the river
Observations great precision wanting on yeloci
ties OF waves of different height shall assume ten feet
per second without asserting yet strongly believing that
this is equal to maximum velocity of % feet The
waves in the Lake seldom exceed this height In such
wave about oneaf of its force is spent above the trough
of the wave and the other half upon any resisting bodv
beneath the trough.
We Should then prepare to resist the force of five feet
OF water moving at the ten feet per second q,
casional. extraordinary periods
Without accurate determination of the STRENGTH of
materials to resist this force let us see what
our wharves are supporting during considerable portion
of the velocity of five per second is not
usual acting the whole length of the piles saw twenty
to forty feet in length This force (fty feet bv twenty
feet at minimum is double the former item feet by five
feet) at maximum.
The wharf piles usually without braces and are
merely secured at the upper lower ends of the niles
They never yield to the pressure of the currents
Many of these are single piers supported by few slender
piles, tied at the top by girders and flooring
On both sides of the Lake along the sea shore there
exist slender wharves and piers that have stood all
ordinary storms and great magnitude rs these
assumed, without yielding in water of five or ten feet
These are not driven more than four feet in the ground
and are without braces or ties of any kind
1t is then plain from experience, that to resist the
force assumed for upon the Lake no very powerful
work of engineering is required
Upon consultation with the most experienced and suc
cessful contractors for ping wharf building ETC. il
GLIDING who has just completed large contract of
Lake piling find them very ready to take contracts Mt
reasonable rates in png for railroad track across Lake
Pontchartran and entertaining not the least doubt of
the permanence of work, such l have prepared to
submit, in another, the last of this series of articles
1t smy intention to furnish rigorous ANALYSIS unon