The weekly hawk-eye. [volume] (Burlington, Iowa) 1858-1860, 1859-06-07
lYron the Rock islander Argns.-Extra. May -
@a THE EKsB REPOkE
TIE BRIDGE AN OBSTRUCTION
The OsflcIa, Docuuncnt.

We present herewith 40 extinct from the re-
port OF the Commissioners. appointed BY Tn
Secretary Of War, 70 Investigate the Rock L.
land Bridge. We give all We have received
| the main points in the report. But there j
enough contained in what We puuhlist below
| 10 sati-fv every one. The Commis.ioners vepo,'
| the bridge a serious obstruction! All the cham
pagne, expensive suppers, railroad excursions
nice talk and attentions lavishe5 on the Com
Mittee by . gentleman connected with The
Bridge Company, have had no influence The
bridge is an obstruction! Read the Report =
Extract from the Report Of the United State,
| COmMsxxiOneTa, sent 10 ErGmins tie Kali
road Bridge AZ kock Island.
lst. The Board is Of Oplnion that the railroad
bridge which crosses the Mississippi River, be
| tween Rock Island aud Davenport, is not con
structed accord ding to correct principles, re
terence being had TO The interests Of bayiga-
ton.
End. The piers Of the said bridge are not oi
| the best form, and there vas no practical diff
Guilty in constructing them OF the proper form
With the exception OF the turn table pier, the
Board is OF opinion that the detective form ol
the piers is q matter OF no material import.
ance. The turn table pier will be more par
| ticnlarly referred to in answer TO the next
question.
Srd. The only pier larger than is necessary il
the turn table pier. This pier, in the opinion oi
the Board, should have been constructed no
longer or broader than was absolutely necessary
to sustain the truss, when the draw il open, aud
protect it from injury by passing boats. Il
might have been constructed with q length Of
1896 feet, sffording ample support aud protec
ton, and beng actually 355 ieet in length, the
difference, 50 feet, is unnecessary, and iu the
judgment Of the Board pernicious. The effect
of making 1t larger than was absolutely required,
Is tO contract the water way, Increase the velo-
city, harrow tn. draw passage and present more
surface tor boats to striAe against; thus III !
crsaslng the difficulty OF their passages through
the draw. In y pier VI this size the form OF the
starting 10 Of Importance, and the upper faces
o the pier should have berD curved surfaces.
4th. The piers are not placed parallel wnh
the current. but at angles varying IRON rs
degrees to l4} degrees. The feet OF this obl,-
qulty Is 10 treble the obstruction 70 the fvw OF
the water, and consequently to sffect The in
crease OF velocity il the same ratio. Another
consequence is, that the passages Vi steamboats,
and RATS through the draw and between the
piers, are rendered much more difficult and
hazardous. Furthermore, the draw on the Iowa
side is rendered useless by the formation there
in Of an eddy.
5th. Tie s.locities in the different parts OF the
river III the vicinity ot the briug-, have already
been stated, aud will be found labulxted in ap.
pend,x co.
9th The edd, on the Iowa side OF the turn Ia.
bic pier, ~ nearly AS could be estimated. L.
about ltU teet wide 1T the foot Oi the pier, ard
the turbulence in the boiling OF lhe water, ex-
tends about 5uU feet below. This EDDY, how
ever, is constantly varying its position aud
Al IT. M..c,. -, ~. q, bo.,.
ascending ahd descending. is u. ..dooat~diy 70
render them more difficult, on account uf tie
care required to avo,d getting On. part Of the
boa, into II, while abOthrr par is in THE curreit
OF the draw. 1t has been previously stated thai
The fleet vi this eddy in the Iowa draw il u
renutr II useless.
7th. The surface OF the water at the up stream
end oi the turn-tab--pier, is l6& inches above
the surface OF the water ut the down stream
end. The extent OF the back water or reMous
nearly as could be estimated is about l5U
Ieet.
9Th, the Bridge is badly located, and 10 con-
sequence OF this bad location is a greater OBJ
sfructioa to the passage of STEAMBOATS, thsn
would have been nee, ssary, had the location
been good ANY site liz the vicinity below
Rock Island. out Of the rapid current, would
have been better.
:" The Board considers it proper to recapitu-
late some ot the well-known principles OF Bridge
building to show how far Trey have been con
formed 10, or departed from, with the Rock Is
land Bridge.
These principles are =
lst That given place in locating Bridge
over any stream, the site where the veloci.y
OF the current is minimum, should be selected
I'd. That in designing bridge, the piers
should have the minimum cross section consis-
tenl with the supper, OF the snperstructure, thus
Offering the least obst, uction to the flow OF the
water, increasing the velocity OF the current a.
little as possible,
Sd. The piers should always be placed parallel
with the thread OF tie stream. Tor the same rea.
sons as those stated in the second principle, and
because they thus render the passage Of boats
and rats less difficult.
4th 10 design ng bridge over q river hae
ing q large commerce in boats and RATS the
draws and spans should be OF the greatest
practicable width
In applying these principles to the Rock Is
land Bridge, the Board is constrained with ex-
treme regret 10 report that all have been vic
lated /; thus rendering the Bridge not only an
obstruction to the navigation OF the river, but
one materially greater than there is any occa-
sion tor"
EN- -anneR pm saG m n - NJ aR,o Tnr,>u6~