New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1894-09-17
CHIC KEKINU q SUM,
100 Fifth Avenue.
SELECTIONS FROM THE MAILS
TILT NORTH RIVER BRIDGE REPORT

r..
ryctXEERs CHARGED WITH IGNORANCE OF E''f''
MrNTARY FACTS IN HYDRosrATIcs
To the Editor OF The Tribune. -,,
sir. In the report Of the Hudson RIVER
commissioners published In enc of the SUNDAY
n,nors Of last week | find it explained that '"'
weight of the piers for that structure was .no
nutod by them by deducting the W''S"' VI Wv
material which they would displare' lor eN'"''
the masonry. which in air would "e'sn '"' PO'
nor cubic foot is held by them to weigh III "'','
eghty-seven pounds in mud fifty po"h"s anu ~
so,d thirty mounds. II there were any way "P
narent to interpret the statement aS "" -,
the printer I should hesitste 10 p'"c'' '''''
couId have been made by "A company or s'"'''"'"
,h, ho,e ., their tongues' end all the resources
Of modern engineering; but the same se"'i'i'"
are in the very fact OF making inns rFPo'l'
,,,o1 :, an effort the success OF which seems az
present Inevitable. to inhct upon inc cry u
York a frghtfu calamity, anu 10 u" ""' " "
enormous cost under the foolish pretence Oh pehe
o,ine us commerce. by measure which MUS.
inevitably add largely to the present tNP'"'. Va
ST., fre,ob, and passenger trafic; besides lhrlc'-
,,r a shameful Disagreement upon the city. Inc
two facts are so entirely congr1ouS WIN enc"
other that difficult II might be 70 pel''Ve '''''
~ them Of rational men, when we KIN" "''o
%, thcm 10 be true the IL quite clear TOT oe-
,iev,ne the other. Naturally enough o'"'" "
Gentlemen who could era vely abet the expenditure
of go ooc 90 10 500 $4,000 In building pfldse "''''
,, o,,rlo,od must be- worth vastly less than
nothing mistake the meaning OF simple principe
~ hvdrostatcs I'm making their CALCULATIONS
cubic foot Of masonry which In air "ond
weigh $50 pounds If suspended In water "''s"'"s
90 hounds per cubic foot would weigh 50 pounds
and the same would be true proportonaiy OF any
heavier medium. and In mercury TN" SANE o'o'N
would float Ike cork In water. but II "o'S "0'
follow that the same would be true oil 'o"''
l,id In cement upon rock. Water could not lessen
b
,rder side. and n nld I'm cement there would De
no water upon under side. and no pressure ana
ia weight would be the same as IN ar 10 mat
ter whether this surrounding material i"s"t w
water MID sand or mercury. 10 h'usrd''' TAM
thin tumblor which when put In water bottom
down floats with more than its own w"ieh, o,
,y,ter inside. that ,s weighs less than one-hait
IT, bulk Of water put this. top down. III an '"py
pail the bottom Of which has ne'h spIs't ", re
a LAYER OF cement laid just thirk en9usn 20 p,.
~ 49,. water from passing under the tumhlers
edge when the pail - hlIeI on ,,,''t -, I've hot.
,oo, and the weight OF the material which 1t as
places will have no tendency 10 raise II ,.,,
nut astonishing as T. f. nat ratinnpe d miSu a..
derstand.ng OF simple matter sh'l.n nv H.
way into formal rcpor; of PHa-i l"a ATM f., ~
~ engineers. this r. not all TINS eNp'ht'%n = ~,
,.r.I -. 4 means ~ determining on" ~ ~" da'a
from which 10 compute the s,rnh s ai,m ~" tb"n,
4, wore trur ina, the weight of material displaced
&. to Dee deducted from That ~ ne 1oH,r '' hn,
sow could that lessen N" strain upon the masonry
her. bet
,ovy.r9 Take the water and other surrounding ma
,.,l,I AWAY and tho eutir. weight woulh De NuS-
tainci by the BEDROCK foundation but being IN
nlace this material would lessen the weight or
he masonry only by ~ upward pressure upon us
,l.r sie The external pressure upon the ma
s,rry would then be caused Just "a II was before
hy the weight u all the sup"rncunbrut ihat''!tI.
~, ,g,ln IN. masonry from n" BEDROCK u" IN"
surface Of the water Is inclos"I In ron cyi'FS,
,rI -, long as those cylinders holl supported AZ
,h.,. are hv the pressur" - the mui ana sdiii py
which they ar. surrounded. the strength OF me
,r,s,urv which they lnclo9c - pracu'hlF uNttA-
i.eI prevent It's escape from IN" cyUui"r ana II
you'll max. no difference 20 the STABILITY 81 me
nrtIy. whether IL was masonry AT an or only
,,,fer How then. can Il hr necessary 10 nhNr
.sneriallv good masonry IN these cyllnn"rSt w I'm
no caet-ron cylinders ~ sufficient strength 10
h.or the strains incident 20 con-'rlcon supported
hv an external pressure u ten tons per square
loot II would Doe interesting 10 hear our IcattHel
f,IcnIs the advisory board explain how an'thns
nor. than filing Of broken stone am Sini ccud
he necessary sustain any posS'bl" weight OF '"'
brdg" -, ,..,,t.. t.,l.s..l l,,. tho
most crrsorv elimination ~ thiS very imposing
I'cumen, What might he discovered upon closer
,sr,r.nn may BE- LETT to conjecture. but Whatever
ma H.. We need not be surprised AZ anything
10, ~ a rational defence - scheme "hlch runs
n,o,cr IN fact and reason at every point
''"''''' " : II. WILDER
y.y.rordon. Conn. sept II, lSi