The daily union. [volume] (Washington [D.C.]) 1845-1857, 1857-02-13

.ye 10 some questions Of hydraulics applicable to
- process excavating the earth for gold mining
soIy received and in conformity with the usages Of the
Institution in such cases II referred 10 Mr. Charles
E1st IT, gentleman in whose knowledge and judgment
~ this ,s we ena roa Es
which, th gives vefy full aud satisfactory answer to
all your inquiries.
Vs. am, very truly, your obedsns servant.
Secretary Smithsonian lnsu..S1tion.
wAsHIsaros, d. c., January II, 1857.
DEAR ss lin reply Mr.. Clngmans inquiries submit
The following dlcta, which canne take tme 70 aenonsae
bscanals Of which Mr. O. SPEAKS should be placed on
the hi1bsst level the ground will permit-that 70 'aSi
the slope Of the canal should gvs.- DC very Small anu
The power of the should not be wasted in
scent in the hope Of economizing in the cost Of
good wide ditch rough ground will very lit
tie more than small one of the same depth.
The of water Is generally the product of the fall
or effective head into the volume discharged. But in this
particular application cannot admit that principle and
am Of opinion that the head being constant the effect will
depend much the OF water discharged by single
ppe in other words that will be found better to dis
charge through the largest manageable orfces-tbat
greater effect will be produced by the column discharged
from one pipe of two inches bore than by those from
pipes Of Inch borethough the volume and velocity
are the each To obtain good results requires
large concentrated masses Of water.
Ii makes difference whether the conducting pipes
leading from the canal to the orces of discharge per-
pendicuar follow the slope of the ground at least the
difference be reduced to very small quantity What
from the canal to the orifce OF discharge.
If these pipes are OF leather canvas or guta percha
they may burst made arge or they will offer great
sance to the Cow OF the water through them II they
are too small But this Is practical difficulty easily
come by substituting cast wroughron pipes for
this purpose which can be put together rapidly and
shifted about easily.
The lower end OF these pipes should be furnished
with screw nipples upon which the hose could be readily
attached They should be furnished with cock also, for
The following calculations meet the cases submitted by
Mr. Cngman assuming his canals to be of rectangular
sections:
Slope feet per nemean velocity IL feet per section
!. { s.
The volumes delivered by this ditch, and with these
slopes, will he--with slope of
feet per mile--lyso==l5.s cubic feet per second.
25s9=225
32s9-288 /"
3.7A9=-33.3 g.
But if the dimensions Of the ditch six feet by three
feet the results would have been for the velocity
slsspss feet per mile-vseety q feet per second
IS AZ
slope Oh
. feet per mile-2lsls==37 cubic feet per second.
- g" 3.1sls=-55s
6 g 4Osls-@720
8 46sls==S2S HsaH
Mr. Clingman should observe particularly these facts
yiy. E Y Il . F E 3 b
The larger ditch six by three with fall of only two
feet mile win convey thirty eight cubic feet Of water
The smaller ditch three by three with fall Of eight feet
per mile will only convey thiryhree cubic feet per sec
end.
The large ditch with the small fall carries some15 Del
cent water than the smsl ditch with the great fall
Again the total head to be used is supposed TO be lOC
feet, and the length Of canal 10 mes.
The larger ditch with fall of two feet per mile delivers
its water at an effective height of
l00~-lON2=8O feet.
The smaller ditch, with fall of eight feet per mile de-
lvers its burden at an effective height of ..
1OO-l0s $40 feet.
II wished TO compare the relative powers of the water
borne by these dtches should express them by the
headsassuming, Of that the water in each
would be discharged through critics. OF equal size
The power Of the smaller ditch would be expressed by
The power Of the larger ditch would be expressed by
The larger ditch would, therefore, do more than fou
though it is only twice large the smaller. ...
The discharge of round orifce, ono inch in diameter
under aa
head Of 80 feet will be l471ooo of cubic foot PEI
second.
head of 60 feet will be 2l5ooo of cubic foot PEI
second.
head of 80 feet will be 100000 Of cubic foot pei
second
head of 100 feet will be 267looo ola cubic foot pei
second
ditch of rectangular section, six feet wide and three
feet Deep with slope of two feet per mile would deliver
above 80 cubic feet of water per second As each pipe
with head of so feet would discharge $40 1000 of cubic
foot per second this ditch would keep in action 3s 1000
24O==l6o pipes of once inch bore.
This system of working the gold mines must be very
eecua But great deal of its will necessarily
depend the skilfuness OF the entire arrangement.
In my opinion every should be observed to convey
the largest of water attaiDablp to deliver it at the
greatest possible height and to discharge it against the
soil 10 be washed through the largest manageable pipes
There are many practical questions connected with this
business which should be considered but they depend
their solution on the shape of the ground, &c
Some allowance must be made in the calculations for the
necessary loss of water the way from the stream to the
dggngs but this loss will depend the character of the
SOIL
II the soil is argillaceous it would be advisable to form
basins the line of the canal wherever it be done
without adding materially to the cost.
The water ought not to be drawn directly from the shall
low canal into the pipes which convey it TO the or6ces
discharge There should be interposed large iron pipe
pensock the canal, If the ground permit should
oe made very deep at that point to force the water
INTO the pipes under sufficient bead.
Short bends in the pipes should be avoided The larger
e pipes and the clearer they kept from all SORTS OF
obstruction the violent will be the discharge and the
better the results
1t not mprobable TINT II will he fouud advisable To