New Orleans Republican. [volume] (New Orleans, La) 1867-1878, 1875-02-14


interests involved in the question. The go'
ernment has expended, and is still expent
ing, large sums of money in improving tn
navigation of the upper Mississippi. Nilsson
ri, Illinois. and other rivers, for the expres
purpose of allowing the largest steamers t
navigate them. It acould. therefore, see'
entirely ont Of keeping aciM this genert
policy to alloac, at the ref'y threshold of nes
Improvements, a structure which ,could pra'
ticaily debar large proportion Of eristin
steamboats, from using them.
The board are, therefore, unanimously Q
the opinion that the bridge, as at presen
designed. will prove very serious obstrnt
ton to the free navigation OF the MississipE
| river.
| Under these circumstances the board d.
not feel justified IN recommending an,
change which would involve q cOmplet
remodeling of this magnificent structure
now SO nearly completed. At the sam
time, as already stated, they deem 1t absO
lutely necessary that some provision shOult
be made for allowing large boats to pass tn
bridge with safety whenever they find i
necessary to do SO.
| They would, therefore, recommend, as th'
most feasible modification, a plan whicl
has been already tried and found eficien
at the railroad bridge over the Ohio rive
| at Louisville, Kentucky.
| Leu d CaUGl, OF TdtucT au Optu cut. IN
| formed behind the east abutment of tn,
bridge, giving at the abutment clea
| width of waterway of 100 feet.
Let this opening be spanned by draw
bridge giving clear span of l2O feet il
width.
BY this plan boats as large as any nov
built would be able to get through thi
bridge in any weather ard at any stage q
water, and only at the cost of some littl'
delay.
Of course our artist did not like the re
| commendation of the board any better thar
he likes .jetties at South Pass. Of course h,
| criticized the report Of the board in hi
usual effective manner, and all the st. Loui!
newspapers cried "Bravo " as they are il
the habit of doing 80 at every exploit o.
this wonderful engineering genius. Sucf
an outcry was made about the matter that
our Great Father called on the board for ar
explanation and got it in tho shape of ar
able and thorough report, from which We
extract az follows:
As the review of Mr.. James B. Eads
chief engineer of the bridge company, is
one of the documents which have been
referred to the board, they make the fol
lowing reply to such portions Of it as seem
to require an answer:
Mr.. Eads quotes from the report of the
board:
THE apparently unreasonable height and
size Of the chimneys in general use on these
western river) steamboats, are really essen
tial to secure good draft to the furnaces
and economical combustion of fuel. Arti-
fetal means to produce the same end are
generally very expensive and often inetfec-
tive"
He then goes on to state:
Nowhere has the economy of fuel been
so closely studied as in the construction of
ocean steamers"
In this statement Mr.. Eads is entirely in
error. Economy in fuel has been chiefly
studied in connection with land engines,
especially those used tor pumping. Here
there is no limit to tie size that can be
given to the boilers. and by using very
large evapOrating surfaces and slow com
bustiOn, great economy IN fuel has been
attained.
The mechanical effect due to the combus-
ton of pound of coal, generally expressed
by the number Of pounds raised one foot
high in a minute, is alone considered in this
case, the time required for combustion
being ihmaterial.
But if from any cause the size of boiler is
restricted, while the same amount Of me-
chanical effect is required, it is manifest
thai the element OF time must be consid.
To drive large ships at high rates of speed
requires powerful engines and boilers,
while the room allowed for the machinery
is kept as small as possible. Marine boilers
are therefore necessarily very compactly
built, and maintain a high rate of cOmbus-
tiOn.
In their construction efficiency in supply
ing steam with sufficient rapidity is the
ruling consideration. Economy of fuel,
while still Of course important, must and
does give way to it.
Artificial means are seldom used on
them to produce q draft, and although
the largest ones consume much more fuel
per day than any Mississippi steamer, none
OF their chimneys approach the height OF
some of those on the river"
The statement that 1.-The largest ones
consume much more fuel per day than any
Mississippi steamer" is certainly unde-
niable. As the engines of the larger ocean
steamers work up to COCO or 700O horse
power. while the largest ones on the Miss
ssippi probably never run higher than
5000. it is not surprising that the fuel con-
sum ptiOn per day "a greater III the former
case.
Ii, however, Mr.. Eads refers to the rate
IF combustion-that is, to the number of
pounds of coal burned on square foot of
rate per hOur-then he is again in error.
On ocean steamers this rate is from six !
cen to twepty-t five pounds, while on Wes- |
ern river boats it runs from twenty to fifty |
bounds.
The next statement, that "none of their |
himneys approach the height of some of |
hose on the river" is specious and decep- |
i've as well as erroneous.
Persons who Judge the height of an ocean |
teamer's smokestacks from that proportion |
# them which they see projecting above |
he upper deck, may we'll infer that this |
leight is small when compared with that Of |
he chimneys of some of our river boats.
But it must be borne in mind that on the
cean steamer the boilers and furnaces are
ocated deep down in the hold, SO that
arge portion of her chimneys are hidden
" the hull, and the actual height, measured
rom the CRATES to the top of the chimneys,
nay be very respectable. Still this height
nust always be limited, first by the depth
f hold, and secondly by the height to
which it will be safe and expedient to carry
he chimneys above the upper deck. very
reat projection would cause much resist
nee during head winds, and the chimneys
'ould be liable to be rolled overheard in
eavy weather.
As Mr. Eads formerly commanded river
rossed the ocean, he certainly should have
nown that he was comparing things
hose conditions were in no way alike. He
oes on to state:
1.-The great development of power wit
essed every day in locomotives whose
never exceed ten or twelve feet
/ length is obtained without any artificial
leans to produce draft except by the
scapement of their waste steam"
To locomotives the same remarks apply
) to marine boilers, but in a still greater
egree. Lightness and cOmpactness are
,e essential qualities, and all questions OF
economical combustion must be subordi-