, 1873-11-11

|
this result.
LAKE HARBO1sS.
Meeting OF tho Engineors' Club OF tho
NorthIvcst.-An Instructive Pnpor OH |
Luke IIarbors Rcnd by Col. houston |
..Artificin1 and Natural 1Rnrbors-- |
Construction OF picrs md nrcak- |
yyntcrss . |
Tho Engineers Club Of tho Northwest held q
regular monthly meeting ut the Academy OF
scionce last evening, President chesbrough in
tho Chair. There wero ton membors pres
ent After tho transaction Of como
routine business, Col. Houston, U. s. A.,
road papor on lako harbors. He aatd
the improvements on tho great lakes which
have boon carried on 60 extensively during tho
past few years, to tho great benoat of commerce,
| had assumed, at the present time; tho character
| of systom tho principles Of which it was tho
object of the paper to atato and illustrate IN
| part, Tho lako harbors were OF two clasaos:
'~et, thoao which we're entirely artificial, aud,
H. thoso Which nere in part natural ind In
aecorlA, al. The first embraced those whore
part artthu. whatever was Afforded against
ny protoctlon winda by tho line Of tho
preeallng on-shofs 'ts, in which oaao all tho
nro,ection afforded was b, ,ta.,ona IN tha
second embraced, first, inde. tro,n certain
coast which afforded protection n,rtin1
winds, but not from all, and required ,vora
protection; and, second, natural tnlets OF +.
which required improvements to enap!e SeesulH ~,
Of the larger class to enter thom ea1ely' uuo
general principles involved in tho oonstruoe'ou =!
1or tho first olnss OF harbors, md tho hrst ~
o;aon Of the second class. conHiat tod Of epcos,
3,o vstora to he protected by barriers called
s 4sestwators, upon which the force Of storms rs
1o ID be a5psnqsa so tSo SeFy ygras ses ~ Ed
rive, e%9ty!as 9a9Gme 'e' Of I discharge to maintain
ciont, 7v ,t,el into tho laEo Of sufficient
eha. depth to accommodate tno "thsa ehss
oasM a. traaaa aIe tba %as volnmo ot dis
except 10 tin I'll that tho direction ct the cur
charge s 80 sn It varies constantly With tho rise
rent A. at the 3 mo9 Tho lake surface was N
constant state Of snS froauoncy as to give
cauBes Of such oxten. Tic streams emptying
to the lower portion. o. Of tidal rivers Teae
OSCILLATIONS were sonletir. w. "a 81 to extsnt and timt
feot but they werc irregula. Of foot was quite
Of occurrence An oscillation 1tleHe mouths ant
frsauon G o. a. r.
% chanpel out to Tue deep water Of " WI T Channel ann
royotting the sides Of the excaE, :althern por
Tho principal storms affecting tue 'igsp wer
from from tho O. northeast Tho waves G. 1' T. a,,;
struck the shore at On angle Of 45 degre> 9nnrl,
| produced q strong lateral current in . hou' 1r6
| direction. The material Cd or near the 81: Vi
| Of the waves, was stirred up and moved to the
south. Whom it met tho mouth OF stream
| It WAS carried ont and depoaited on tho north
side Of tho channel 50 thas @ aanh the onSRhs M11st
| natural channels did exist wore crooked, and liz
| Bio to change by the action Of stormB. During
tho season OF 1872, there was only one stream ;tn
on tho west side OF Lake Michigan and on Lake
| xu5,n hnr fT0rroY1u1GUtH
progress, which had q constant outward curront
at tic mouth. This was the Menomoneo hiyor,
in Michigan. The channel, when intended 70
DO not lesB than 600 feet ip width. The direc-
| ton given to the channel had generally boon
perpendicular to tho Bhoro, and that WAS, perhaps
theibeBt, excoptin special casos He regarded tnia
entorlug the mouth Of the harbor, whoroas, II
|.the distance between tho piers increased toward
k}tho ahoro, tho Sea would be reduced immediate
lily after passing the heads OF the plers:
,, Il The pierB and breRkwaters in tho lakes Wor'
}3oonstrnctsd either Of cribs OF timber aud iron
| filled with stone, or Of pile-work. They were
. | In q certain sense, temporary structures, re
, quiring frequent repair. The work under water
III put together 80 az to resist tue forces t.
( which it was subjected, might bo considorod Per
! mauent, Us timber under frosh wator Woul
last indefinitely. Above water, tho tlmbo
would lust from ton to fifteen years
It was impossible. except under the most fa
= thoir plnceB on tho ordinary lake bottom wttor
d preparing substantial foundation, OF loot
a stone. Tho first crib in the Chicago broakwat!
i was placed at tho north end OF the york, !:
i twenty-four foet OF water. Three months ate
- wards, during hoayy northeast storm, IT noye
t bodily to tho north about twelve foet, and to tt
T. cast about ono foot. Crib-piera, when place
o IN good alignment and oloao together, mako
III vory satisfactory and substantial work. +
~ thought 1t would DO an improvement on Il
,oH present system If tho cantrc Of -, Il
ii: crib, dividing 1t 1engthwiso into thr ns
ia tom aud partitions put in to hold Il
~ Stone over this portion. When large orlba
~ timber filled with stone were uset It was impe
of tant that tne 1oohdAtlon gu WHICH, ~ t,1uy ,;nd.
" mine. The form Of broakwater winch seems
~ bo most suitable In the general case consisted
~ a wall, the sides OF which had a ellght patt'
st | placed on foundation Of rubblo-Btono.
n. After thanking tho Colonel for roadlnR tho
Ii | nar tha Qlnb adiDurnnl.