The New York herald., 1876-12-17
THE BROOKLYN BRIDGE.
Mr.. Albert Hill on the Mathematical Accuracy
Of the Specifications.
Colonel Paine on the Progress
OF the Work.
A Startling Statement as to the Value Of the
Tests Just Completed.

In by the bidders for the 900 pounds contract
~ last completed and their report vii, be sent i'm
nedately for the consideration OF President Murphy
and his Board OF Trustees. Mt Albert Hill does not
uppear satisfied with the way that work has been done,
lnd in an interview with HERALD reporter, qres
ions the accuracy OF the figures upon which the spec
icatons are based. He demonstrates mathenatically
irst that 500 pounds, and not g. 400 pounds is the
:orrect ultimate breaking strength corresponding 10
loo, 900 pounds per square inch OF solid section in
No steel wire; second, that most OF the samples
submitted for test exceed tno weight OF II
feet to the pound, required by the specihca
tions from seven 10 nine per cent, and
are also less In OF the
prescribed diameter thus diminishing the number OF
wires increasing the weight OF the cable without
showing a corresponding excess Of tensile strength
and last hc points ont apparently garing
in the calculations by which the total stretch is OBJ
snned
VISIT TO ruE woRKa
Yesterday afternoon HERALD reporter paid visit
70 pier 20 East River finally found Colenci Paine
Of the engineers in charge of the works. The fol-
lowing conversation ensued:--
RxPoRrgR--win you please give any nforma
Non how the testing OF tho wires is progressing
md when you expect to finish it?
Colonel PAISE-we have alrcnay finished all the
tests that to be made
kEPOkTER-davo tueSo tests Decn attenued Win
satisfactory results?
Colonel PAINE--Some have and some have not, but
beyond that general statement say any thing
more
REPoRrER--Can you give any statement as to
the results Of these tcs,sy
Colonel PAINK-I cannot Every wire manu- facturer
who has had his wire tested by has been present
and taken copies OF the results of the tests But it
would not do for me 10 give you copy OF these re-
,ults before have unicatcd with those au-
lhorizcd to make the tests do not withhold this
information from any unwngness to oblige YOU or
the HERALD the pubhc but as a matter Of strict
professional duty my part toward those who have
the first right the knowledge The have been
madc as publicly as the wire manufacturers themselves
have permitted.
REroRrEE--when will you report tho results OF your
tests TO the Board OF Trustees?
Colonel PAIyE--I report them the Chief Engineer,
and do not know when ne Will present the report
the Board They have meeting in a few days and
do not anticipate any delay.
REroRrEg-Do you think the contract will DO
awarded Monday next?
Colonel PAINE-That would be merely private opin-
sther.
REPoRrER-1s there anything new to say concerning
Tho progress OF the work on the bridge.
Colonel PAlNE-I don't know that there is. part
the preliminary work has been delivered and all tho
details OF the machinery for the stretching OF the
blcs are progressing rapidly.
REPoRTER--Have you anything to say In regard to
Mr.. HilPs statcmGDtsy
Colonel PAISE--Nonc OF tho engineers on the
bridge that aware OF have said one word in re-
gard 10 Mr. Hill, pro Tncy not personally
acquainted with him, and have made statements in
answer 70 him, nor have they any TO make. Colonel
Rocbling Mr. Martin and myself have had the charge
Of the wire work this bridge, and we have neither
said nor have anything to say on this point.
IyTkIvIEw WITH MIR. HILL.
A HERALD reporter paid n WISH yesterday afternoon
TO Mr.. Albert Hiil at his Office and obtained the Io-
lowing interesting interview
RKPORTER--I have called, Mr.. Hill, to you in
gard to the tests, you told me when they we're
pIecd you might perhaps have something 10 say about
Mr. Hull do not know that all the tests arc fn
ished; ut the time have here OF
the results OF about seventy OF them. You remember
interview that believed that these tests
would probably form no true criterion as TO the quality
anu ultimate strength OF the material used. i
Eore uy satisfied than eyer that my hrst impressions
were correct
REpoRrER-why you more fully satisfied
that the tests criterion OF the quality and
ultimate strength OF the materially
Mr. HLL-Simpiy because have since then taken
the timc and trouble only carefully revise
rccalcuate the results OF the tests as obtained them
from day 10 day but 10 investigate the correct
ness OF the fundamental formula which formed the
basis Tor Tho specifications.
RkPoRrER-Mr Hill, have you any objection to give
statement OF your mathematical calculations and
their exact rcsultsy
Mr. HILL certainly have objection TO giving
you some or them, but thlrIkes me that the HERALD
would hardly willing to throw open Its columns
purely scientific discussion although the points at
issue do not rcqrrc any extraordinary proficiency III
RKpoRrER-The columns of the HERALD open to
every discussion IN which the public interested.
whether political, religious scientific or otherwise.
should like to have your views on the question?
Mr.. Hill am at present preparing pamphlet
which intend to submit to the American Society OF
Civil Engineers for discussion. have objection to
tive you such portions OF II think night be OF
REpoRrxRoI shall be very much pleased to have
rou give the HERALD any statement on subject which
but be interesting to the taxpayers oi the cities
pf New York and Brooklyn.
ERRoR IN THg FUNDAMENTAL FORMULA.
Mr.. HILL-ro begin WITH article OF The speci1ca-
lions for letting ui December reads:-"Each wire
must have breaking strength OF no less than 3 400
pounds. This corresponds III wire weighing IA feet to
The pound Of 160 600 pounds per square inch
OF solid section The elastic limit must DO no less
than 47-lOOhs OF the breaking strength, or 1900
pounds Within The limit oil elasticity must stretch
IL uniform corresponding 10 modulus OF clas-
tcity OF not less than 27,Oo0 0c0 nor exceeding
20, 900, ,000 The quality Of the wire in regard 10 ITS
stretching s iurtner ailuded to under the head OF
sTcsis y Now, unfortunately, an ultimate or break
ing strength Of 3,4oo pounds IN No.
steel wire Weighing IA feet the pound does
not represent ratio Of Loo, 600 per square inch
Of solid section. This breaking strength OF 3400
pounds is, according TO the specifications obtained
by IA equals 40i3 plus. or in round numbers y 400
pounds. The defect IN this formula arises IRON the
Tact that It prcsupposes the weight OF every cubic
loot OF steel offered Tor weigh 49, 81 pounds,
which could be only the II all the different kinds
which is obviously practical impossbility. The
derivation OF that formula IS us fol-
weight OF steel al 4s3s4 pounds uhe correctness
Of even this figure dcbaablc) then u cubic foot of
steel weighs "a lbs, then one inch square one
foot long weighs 4S 81 divided by la equals 3 6 and
II inches long welgh X 36 therefore, II we
say rod IL feet long weighs b., us cross section
must no 1 divided by & 10 multiplied by L. and the
ratio breaking strength 10 that Of square
Inch OF solil mst be l60, 600 divided by 35
multiplied by H. But No. wrc. Birmingham gauge,
has diameter Of l65 .siu .170, which corresponds
10 of section OF square multiplied by
3 IA, divided by 4, equals II square multiplied by
B14, divided by 4, equals .o22d Now substituting
this area, which Is the true area we obtain the ratio.
100, 900. divided by o226 equals 3,6l6 or IN round
pHDjers 3. GOO pounds The correct ultimate break
ing strength, corresponding TO leo 900 ponnas per
yQuare inch OF solid section IN No. Steel wire.
CHARACTER uy WIRES TEsrED
or course this II only theoretical REORGANIZATION
oil the insuficicncy Of assumed breaking strength
oi g. 400 pounds. But, though am not prepared 10
vive you tnbuated statement OF The weights ana
The d,amccrs vi the wires submitted for test, can
Jay here that IL will bc shown that their average
weight and aIamccr exceeds tho primary requirement.
ncn Innf mil W. A.