Richmond enquirer. [volume] (Richmond, Va.) 1815-1867, 1854-01-17
TO the Editors of the Enquirer,
BRIDGE OVER THE POTOMAC.

| RlCHM0SD, Jan. IL, 1854.
herewith furnish you brief outline OF the plan Tor O
Bridge the Potomac In lieu OF the present unsghty
and Imperfect and the subject OF erecting
new one hos been for lime past entertained, avail
myself OF that circumstances submit, through your me-
dum the following plan for The consideration OF Inc parties
whom II may concern
years ago be erected at Clifton, near Bristol in England
bu, was finally determined 10 adopt suspension-but
that is abandoned The proposed bridge was 10
extend from rock rock over tho river Avon In one span oil
nearly $50 feet about 220 feet above The surface oil the
water which proposed 10 erect without the aid OIL hxed
scatodne or centres This plan received The appreciation
az many of the most eminent engineers and mahematcans
among the latter will mentioned the late well known and
talented Dr. Brkbeck who wrote ME the following letter 10
80, FlNsBuRy SQUARE, [osnoN.
DEAR SIR:-Your projected bridge, n It's more perfect
FORM have again examined with grea, pleasure and with
Increased conviction OF ils fitness for the singular position
which it is intended 10 occupy Considered 10 relation 10
its mechanical principles and its sustaining power The arc
which you propose construct is most satisfactory and
will am persuaded, combine Ia higher degree than has
erer yet Effected elegance Rhtness stability and mag
nIude of spau. Nothing can be more conclusive WIN re-
nect 10 s mechanical character than tho convenient and
economical fact that will be erected securely without Gen.
terng; and that the epproxang halves will not depend
any material degree, for hsr own support or oI inc aup
port of any load which may be placed upon lhem on any
resistance Tho vortex Every portion ot each ha Oh he
bridge becomes Is finished bent levers and The whole
OF each half consequently have its power determined
bv oonederng series such levers very eS
tended lever OF which the line OF abutment Is inc shore
extremity 1t s obvious however when The lines OF pres
to considerable extent occurs; and that therefore Inc
diagonal braces occupying the parts oil an ordinary ooge
for he purpose Of resisting the thrust OF the upper poohs
of the arch by their weight alone aord essential support
without loading the arch at all In this appicaon oi Tue
aod sides of the space be found apprehend one ma
1era principle upon which the extraordinary ghness OF
your mode OF construction depends The mot accurate Ut
trn,ion which have been able 10 direct the examination
Of your intended bridge has not enabled me 70 guy
well grounded objection it aud assuming the suthcleney
OF abu,ments both for thrust and traction hc adt
by trial or calculation OF the substance oil every part ana
their uucons and the excellence Of the strong tenacious
elastic lera you propose employ the rRsss ana &C.
curty of the fabric cannot disputed With these views ol
the essential! qualities of tho arch and my admiration oi S
appearance stretching the valley al once oeau
fsl and romantic OF the Avon cannot but entertain very
nrdent wish that they whu the decision may oe
induced TO adopt II. The structure WILL persuaded 90
honor 10 The present advanced condition Of practical me-
chancs and the the Influential inhabitants OF Clifton
and Bristol and will provo ornamental 10 natural
scenery of description splendid as to render almost un
endurabe the ordinary ponderous productions OF o ha'
YOU may succeed the belief not less than The wish, oil
YOURS most 'a''"'u''' GEORGE BIRKBECK.
Mr. T. Motley. ;.,
p SIT has tsan maintained that with an equal weight
asked what would be if the weight were greater
To this Il may be answered. that the strength Wouo III e
same proportion be greater. Expansion ana cohtluc.io
woud of course In such structure as mas oeen poposeu
take place considerable extent; out "nou'
oT eyen Inconvenience provided the junction OF Inc TWO
hslves of The arch were effected with reference TO THIS al
toration.
After this It 10 hardly needu TO offer any further remarks
T will therefore only add, that slpce Inc ABOVE was
wr,en have mado some considerable alterations and I'm
provements. will proceed to detail ne pian, no" Pto
bose which Is 10 construct spans Of l05 feet each end
the enRh rather the width OF e Lver Wouo
allow of u spaus making bridge upwards Oh 1oUo leo oe
and aow ample room at each end for draw bridge tor the