Harrisburg telegraph. [volume] (Harrisburg, Pa.) 1879-1948, 1919-06-14

1aShlOned from artificial stone, that
industry is proving one of inesti-
mable value to the people. Millions
of trees have been spared because
of concrete, and thousands of acres
of fine forest have been saved from
the ravages of the saw-mills because
structures which formerly were
built entirely of wood can to-day
be erected without it.
The Story of Cement
1t is only a little more than half
century since all Americas Port
land cement came from across the
seas-and comparatively little of it
was imported for building purposes.
This did not suit the ambitions of
certain progressive Pennsylvanians
in the Lehigh Valley, who decided to
| build their own kilns, and soon be-
gan to produce cement that
equalled the best that could be i'm
| ported from abroad.
They found cement rock through
out a broad area in eastern Penn
sylvania, of which the Lehigh dis
trict-above Allentown-is the CEN
ter. To make Portland cement
which. by the way, derived it's name
from the fact that it resembles the
English Portland limestone in color
l-alumina, silica, and calcium must
be combined and prepared in a way
that the finished product will set
' according to specifications. Clay,
| quartz and lime in this district are
the sources of these ingredients. al
' though blast furnace Stag and other
materials are used in some localities.
In the valley of the Lehigh river
from Siegfried to Easton are great
beds of rocks, some strata pure lime
stone and others clayey or argilla-
ceous limestone.
! These two kinds of rock are mixed
| in proper proportions and ground to
,impalpable powder. Huge crushing
machines MUNICH hungrily their diet
of stone, day in and day out, pass
ing their grist on down to giant
! grinders having maws filed with
steel fails that fly around at high
speed, propelled by central shaft;
cement rock that substance looks
like flour that has turned dark gray.
While the rock crushers and
:, grinders are busy-whole batteries
of them - the coal crushers and
grinders are at work also. preparing
coal dust as finely ground and i'm
palpable as the rock dust.
The Rotary Cement Kiln
, -, Here another process begins, in
| which long rows of rotary kilns play
an important role. Imagine a hol-
, low pipe, lined with fire. brick, big
enough for a horse to walk through,
, about $50 feet long, mounted on
/ pivots and rotated by cog gears af-
/ ter the fashion of a great shaft.
Into one end pours constant
stream of rock dust Into the other.
driven madly forward by compressed
, air, goes a like stream of coal dust,
/ kissing and burning, as from an in
ferno. In the middle of the big
kiln they meet.
Z The observer is supplied with a
pair of colored glasses; the operator
: opens a tiny door and bids you look
: in. Glowing with whiteness that
rivals the electric arc, you see the
! materials apparently in the process
of turning from solid to liquid; but,
just at the point of incipient fusion,
droplets or nodules of a dark gray
: color, ranging from the size of a
) small pea to that of large hazel
) nut are formed.
These nodules are carried out on
an endless bucket belt, glowing like
} embers on a hearthstone, to the cool
/ ing towers. Here they are cooled
} under forced drafts of cold air.
} Then they go to meet another set of
) grinders, Mo endure the beatings OF
} another series of mechanical fails.
} Literally they are beaten to dust
and that dust is the Portland ce-
: ment of commerce, to which the
/ worlds debt cannot be estimated
: with any yardstick at my command
} Dust Without Waste
The finished product is carried to
large storage bins and then barreled
> or bagged.
, In some plants the packing ma
: chinery is far from the least inter-
| esting part of the equipment. Lead
ing from the bin is large hopper
with an automatic weighing ma
chine. The barrel, with the head IN
place, but having a two or three
. inch hole in the center. is put in
position, a big funnel connecting the
, head -bung with the hopper. Through
this the cement flows until both the
barrel and the funnel are full.
The barrel is then lifted away by
: a machine and set on mechanism
! that may be depended on to pack
l the cement tight. Overhead is a
: shaft made on the principle of that
/ Ii L r.E -. -