, 1872-10-17
THE SAND SUPPLY.
How This Important Item Of Building Material is
Obtained---New and Ingenious Apparatus In.
vented for the Purpose.

vented for the Purpose.
Oae of the most important elements in the re
building of Chicago is ono which is most apt to
be lost sight of-viz., sand, the quality of which
is Of vital consequence in determining the
strength and durability OF our stone and brick
strnctures. In order to secure the best mortar
it is Indispensable that the sand be wholly free
from loan or earth, which ara found largely
mixed with the sand dug in the process Of ezca-
waiting for foundations, so that, If Chicago we're
an inland city, she would be badly off in the
matter OF sand. As it is, the great
lake supplies this important item, as the
eand taken from the shore Or the bed
OF the lake is perfectly stsharp," as the masons
say-thAt is, free from dirt, and containing COM
paratiyely little gravel An immense business
is now done in furnishing sand. Alarge propor-
ton OF it is taken from the led Of the lake just
outside the harbor to the right and left Of the
south and north piers, and also in the lake on
North avenue, where pier has been extended
by J. ?. Farwel1 fe the purpose Of securing the
sand accretion. N both cases the sand is
brought up by an ordinary steam dredging ma
chine and deposited upon barges and towed to
the wharyes in the city. A new plan, said to be-
much cheaper than this, has recently been put
in operation on the lake shore at the foot OF
Erie street by Mr.. J. T. Clarkson, who has IN z,
consists simply IN an endless wire
rope extending ont into the lake about 200 feet,
the travelling along d narrow pier OF about the
same length, with horizontal shlves at either
end for the rope to turn upon, and then return
ing to the Shore the entire rope forming hol-
low square. To the rope at the right and left
are attached the dredges, which are made OF
boiler iron, and shaped like . boat, the bow Of
which operates on the principle Of o jack-plane,
scooping up the aand and water, the latter being
forced out at the top. As one d1edge goes out q
distance Of about $50 feet, the other comes in
with ita cargo Of sand, about half g yard, and is
turned upside down and emphed on the shore by
= team OF horses, and the sand is hauled away by
teams. The dredge is worked by steam engine
OF Is horse power. But one is in operation at
present, but another will soon be attached.
About three and one-haH minutes are re-
CURED for trip, and the dredge averages
ninety yards per day, which, at 81 per
yard on the spot makes q very good business OF
It, as but Blk men and two teams are necessary
to do the work. So great is the demand for the
sand that none accumulates, teamsters being at
hand to hau1 it away as soon as it is brought in.
They contract with builders at SO much per yard,
usually from $1.75 to 50, and as they are able to
deliver eight or ten yards per day they make
good wages After three or four days work,
deep cut is made by the dredge, which is then
shifted few feet, and then brought back again,
the first cut having filed up in the mean time.
The supply Of sand seems to be e2haustless, as
the dredging does not eeem to decrease the
shore accretions, from which, IN former years,
the sand was obtained, but when the land grew
80 valuable the sand was worth more to remain
than to be taken away, and the present system
vas adopted in consequence.