Samuel Washington McCallie.

A preliminary report on the roads and road-building materials of Georgia online

. (page 13 of 22)
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which it is formed, are reduced to 1 3^ inches or less in their great-
est diameters. This layer is thoroughly compacted by passing
over it a number of times a lo-ton roller, after which the fourth
and last layer, consisting of screenings, is added. This, in turn,
is rolled and sprinkled, until it becomes hard and smooth. A
hardened way, when thus constructed of good materia), makes an
excellent roadway, which, under proper care, should last for several

The Chert Roads are surfaced entirely with chert. This mate-
rial is generally put down, in two or more layers, and is thoroughly
compacted by rolling, until its total thickness is reduced to eight
or ten inches. The chert used on the Fulton County roads, was

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unscreened ; and, as a consequence, the surface has, in places where
there has been much wear, become rough and uneven. These
roughened and bumpy surfaces have become quite noticeable, in '
places, both on the Peachtree and the Manchester road.

The Rubble-stone Road^ as constructed by the Fulton County
chain-gang, consists of a pavement of broken stone, similar to the
rubble foundation of the Telford road.^ The surface of this class
of roadways is always rough and uneven ; yet they are quite du-
rable. Where these paved ways have been constructed in Fulton
county, the broken stone generally covers only about one half of the
roadway, the remaining part being a well crowned earth-road,
which is almost universally used during dry weather.

The macadamized road, as described above, is the only class of
hardened ways now being constructed in Fulton county. This
class of roadway is undoubtedly the most economical, so far con-
structed in the county. They are less dusty, by far, and are more
durable than the chert road, and, at the same time, smoother and
more suitable for all kinds of travel, than the rubble-stone road.

The road-building materials occurring in Fulton county are
chiefly gneiss, hornblende-schist and diorite. A diligent search
has been made by the writer, from time to time, for trap dikes ;
but, so far, they have not been located in the county. They prob-
ably exist ; however, they must be of small size, or they would be
more conspicuous at the surface. The so-called trap rock, which
occurs more or less abundant throughout the county, has been
found, upon microscopic study, to be diorite or hornblende-schist,
a rock somewhat resembling trap (diabase), but differing from it
mainly in having hornblende, as one of its chief constituents, in
* place of augite.

The most abundant and widely distributed of the above named
road-building materials are the gneisses. These rocks, differing
only from the true granites in being laminated, are fairly well
suited for road-surfacing, by reason of their toughness.

Typical specimens of this class of rocks are to be seen at a quarry

Sec pp. 14, 43 and 44.

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156 f^Of'fPMEXT, METffOfj, A.\'2, UATEx.ALS. BY CJr.VTSES

in the Cotton States and International Exposidon grotinds : also
at the city stockade, a short distance cast of Grant Park. These
rocks, technically known as biotite-gneiss, arc very plentifTiI in
the vicinity of Atlanta : and, for many years, they have been more
or less extensively nsed, in the constmction of the foundation of
buildings and retaining-walls, as well as for street macadam.
These gneisses are either of a light- or dark-gray color, and are
frequently more or less distinctly banded, owing to the segregation
of the feldspar, quartz and mica along parallel linesw The chief
mineral constituents are biotite, feldspar, quartz and epidote, all of
which are readily distinguishable by the unaided eyes^ The biotite
is quite abundant, forming the greater part of the entire rock-mass.
It occurs, mostly in the form of elongated plates and shreds, with
their longer axes parallel. Intimately associated with the biotite,
and frequently indistinguishable from it, by the unaided eye, there
often occurs a limited amount of hornblende. This mineral is
especially abundant in the dark-colored gneisses, quarried at the
city stockade. The quartz and feldspar of the gneisses are pres-
ent, as irregular grains and imperfect cr\'stals. Occasionally the
feldspar crystals attain a diameter of a quarter of an inch, or more,
and thus give to the rock a porphj-ritic structure. When the
cpidote is as abundant, as in the stone quarried at the Cotton States
and International Exposition grounds, it gives to the stone a
peculiar greenish-yellow tint.

All these gneisses are usually fine-grained, and make a fair road-
stirfacing material. Their durability for macadamizing purposes
is well demonstrated by their use, for several years past, upon the
streets of Atlanta. Portions of the pavement of Washington
street, in this city, formerly constructed of this stone, still remain
in fair condition, after constant wear for twelve or fourteen years.

DKoSCRIPTIon ok Specimens. — The following notes are descrip-
tions of specimens of diorite and hornblende-schists, suitable for
road material, occurring in Fulton county : —

Museum No. 1,575. Locality, the Adamsville road, six miles west
of Atlanta. Qitartz-Diorite, Megascopically, this is a fine-grained

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dark -gray schistose rock. The mineral constituents, on account
of fineness of texture, are not easily distinguishable by the unaided
eye. Microscopically, the rock is seen to be holocrystalline. It
is made up chiefly of green hornblende, quartz and plagioclase.
The hornblende is the most abundant constituent. It occurs in
the form of elongated, parallel masses, and as imperfect crystals
with prismatic cleavage. The quartz consists of irregular grains
with their longest axes usually more or less orientated in the direc-
tion of the schistosity. Pretty evenly distributed throughout the
section, are to be seen numerous imperfect crystals of plagioclase,
which are usually quite fresh and distinctly striated. Magnetite »
pyrite and epidote occur as accessory minerals ; but none are very
abundant. This rock is well exposed in a cut on the Adamsville
road at the above named point. The rock is very difficult ta
break, and is well adapted for road-surfacing.

Museum No. 1,63 1 . Locality, Lakewood. Qiiariz-Dioriie. This
rock is exposed in a cut on the recently graded road on the west
side of the old city water-works reservoir at Lakewood. It occurs
in layers eight or ten feet in thickness imbedded with the schists.
The diorite is a dark-and-white-speckled rock, with numerous
light-colored bands, which give it a schistose structure. The
texture is fine-grained. However, the hornblende and feldspar are
easily recognized, by the unaided eye. The banded structure is
due mainly to the arrangement of the quartz along parallel lines.

Microscopic examination shows the rock to be made up of horn-
blende, plagioclase and quartz, with a few scattering grains of
epidote. The hornblende is of a brown color. It occurs in large
imperfect crystals, frequently exhibiting well-marked cleavage
lines, and often enclosing small grains of epidote. The plagioclase
consists of large irregular grains indistinctly striated. This rock
has been used to a limited extent for street macadam, for which
purpose it is admirably suited by reason of its great toughness.
Other exposures of diorite are to be seen on University Avenue
between Clark University and Lakewood.

Museum No. 1,645. Locality, Manchester road,. near East Points

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Hornblende-schist. Megascopically, this is a dark-colored, fine-
grained, slightly schistose rock. Hornblende, quartz and pyrite
are all easily made out, without the use of the lens. The quartz
is mostly distributed along fine, parallel lines, and gives the rock
a somewhat indistinct banded appearance, when it is broken at
right angles to its schistosity. The pyrite, which rarely shows
crystal faces, is pretty uniformly diffused throughout the rock mass.
It also occurs along the parting planes and in incipient fissures or

Microscopic examination shows the rock to be made up of horn-
blende and quartz, with magnetite, pyrite, and a few scattering
crystals of feldspar, as accessory minerals. The hornblende, which
is the most abundant constituent, consists largely of more or less
imperfectly formed crystals, slightly orientated, and often exhibit-
ing beautiful prismatic cleavage. Its color by transmitted light
is brown, with a faint tint of green. The quartz occurs as irregular
angular grains, frequently interlocking, and often arranged with
their longer axes more or less parallel. The larger quartz granules
contain many perfectly formed, minute crystals, which are taken to
be epidote.

Magnetite occurs in considerable abundance, both in the form
of crystals and granules. It is distributed pretty evenly through
the section ; and it also occurs as segregations along definite lines.
The rock, here described, is one of the most common rocks in
Fulton county. It usually occurs in the form of more-or-less ex-
tensive beds, interlaminated with the gneisses and mica-schists,
and is always well exposed, in the cuts of the several railroads
.radiating from the city of Atlanta. It differs from diorite in be-
ing more completely laminated, and in containing little or no
feldspar. Both the diorite and the hornblende-schists, when the
latter is not so distinctly laminated, possess about equal merit as
road-metal. They rank in durability next to trap (diabase) ; and
in all cases, where they can be obtained at reasonable cost, they
should be used in preference to the granites and gneisses.

Besides the above named rocks, suitable for road-surfacing ma-

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terial, might be mentioned massive quartz and mica-schist. The
former, which has been used to a limited extent for road-metal in
different parts of the county, has resulted from the breaking down
of the quartz veins in the gneisses and schists. This very hard,
but at the same time, brittle rock possesses little or no binding
power. It makes a fair road material ; but it should never be
used, when other material is at hand.

Mica-schist is very abundant in the county ; and, like the
massive quartz, it has had a limited use in road-construction. A
good example of this class of rock may be seen at the quarry, re-
cently opened t)n Peach tree creek, near the pumping-station of
the city water- works. The rock quarried here has been used, to
some extent, in the city of Atlanta, for macadamizing purposes,
but chiefly as a top-dressing. It is a very peculiar stone, resem-
bling a sheared diabase. The color on a polished surface is jet-
black. The fresh fracture shows a dark-gray color with a brown-
ish tint. The texture is usually fine, none of the original min-
erals being made out without use of the lens. The secondary
minerals, quartz, calcite and chlorite, are frequently quite con-
spicuous along shearing-planes. Hand specimens of the rock,
when taken from certain portions of the quarry, might be mis-
judged for massive rock. However, when examined in large
masses or in the quarry, it is seen to possess a well defined schist-
ose structure.

Microscopic examination of a section of this rock shows it to be
made up of biotite and quartz with calcite, chlorite, pyrite and a
few scattering grains of feldspar as accessory Minerals. The quartz
occurs as small angular grains, more or less orientated, and polar-
izing in gray colors. The biotite has a light-brown color, and is
distinctly pleochroic. It is in the form of shreds or elongated
plates, with their longer axes parallel. The section, in places,
shows beautiful miscroscopic folds and contortions. The main
defects of mica-schist in road-surfacing, is a lack of binding strength.

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Area, 269 square miles ; approximate road-mileage, 320 ; num-
ber of miles of graded road, 35 ; number of miles of macadamized
and paved road, 18 ; amount of money annually raised for road pur-
poses, $8,000. The roads are constructed and maintained by con-
vict and statute labor.

DeKalb county has made considerable progress in the last few
years toward the betterment of its highways. The present system
of working the misdemeanor convicts on the roads seems to give
satisfactory results, and meets with the general approval of all the
leading citizens. The chain-gang, as now organized, consists of 35
convicts, under the management of a superintendent and a foreman.
The superintendent has general control of all the employees on
the public roads, and directs the work. He is also required to make
reports to the county authorities, from time to time, of the prog-
ress of the work, and the expenses incurred. For his services^
the superintendent receives $60 per month ; while the foreman,
who has the immediate charge of the convicts on the road, is paid
%jp per month. There are also regularly employed one watchman
and two guards. The latter are each paid $30 per month, and the
former $25. The cost of maintaining each convict, including
board and clothing, is placed at $3.40 per month.

It is the aim of the present plan of road-improvement, to have
the convicts repair all the main thoroughfares in the county at least
once each year, and at the same time to do considerable work of
a permanent nature in the way of grading and macadamizing. In
addition to the chain-gang, all persons subject to road-duty work
from two to five days each year on the public roads. Many of the
second-class or less important roadways are kept up almost entirely
by statute labor.

The equipment for road-working owned by DeKalb county is
quite complete, and cost originally several hundred dollars. It
consists of I Western road-machine, i portable rock-crushing
plant (Champion), 10 wagons, 6 carts, several plows, 6 wheeled
scrapers, 22 mules, a camping outfit, blacksmith's tools, etc.

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The hardened ways, so far constructed in DeKalb county, con-
sist of macadam and rubble-stone roads. The latter are made 12
feet wide, alongside of which is an earth-road about the same
width to be used in dry weather. The road leading from Decatur
to Atlanta along the Georgia Railroad is constructed after this
plan. It has been in use for several years ; and it still remains in
fair condition. The hardened ways, as now constructed, are made
of broken stones after the macadam method. This class of road is
much cheaper and more satisfactory than the rubble-stone road ;
and they will no doubt, in the future, be constructed throughout
the county, wherever hardened ways are desired.

The materials for building such roads are very abundant, and are
widely distributed throughout the county. They consist of granites,
gneisses, hornblende-schists, diorite and trap (diabase). A typical
granite of this county is to be seen at Stone mountain, where large
quarries have been operated for many years. This stone is largely
used for building purposes, and for street pavement. It has alsa
been used to a limited extent for road-surfacing. The stone is a
medium fine-grained muscovite-granite. A stone, very similar to
this in mineral composition, but differing from it in being highly
contorted throughout the mass, is to be seen at Lithonia. It also
has an extended use for building and street purposes. The abun-
dance of these stones, and the ease, with which they can be quar-
ried, make them very important road-building materials, not only
for DeKalb county, but for some of the adjoining counties, as well.

The diorite and the hornblende-schist are very common
throughout the county. They occur generally in the form of
narrow belts or bands in the gneisses, and are frequently well ex-
posed in the cuts of the railroads traversing the county. These
two rocks seem to grade into each other ; and they are frequently
difficult to differentiate without the use of the microscope. They
are all more or less laminated or sheared; and they evidently
have a common origin. The following is a description of a spec-
imen of the diorite type, taken from a cut on the Georgia Rail-
road, two miles south of Stone Mountain station : —

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Quartz- Diorite, This is a black-and-white-speckled, coarse-
•grained, slightly schistose rock, forming a zone in the mica-schist
several feet in width. The chief mineral constituents of the
rock are feldspar, hornblende and quartz, each readily recognized
without the use of the lens. Thin sections, when Studied under
the microscope, show, in addition to the above named minerals, a
-considerable amount of epidote, which appears to have originated
from the breaking down of the feldspar ; also, a few shreds of bio-
tite and plates of chlorite. The hornblende occurs in the form
of large, irregular, green or brown plates, usually exhibiting beau-
tiful prismatic cleavage. The feldspar is more or less completely
broken down, and only occasionally shows distinct continuous
twinning striae. The quartz grains are frequently fractured and
show uneven extinction, which is evidently due to the movement
-of the particles of the rock, since its consolidation. The diorite,
as here described, when fresh, possesses all the essentials of a
:good road material. It is much more durable than either the
granites or the gneisses, on account of its superior toughness.
The hornblende-schists of DeKalb county, when not too distinctly
laminated, are also preferable to the gneisses and granites for

Trap Rock was located by the writer at only two places in De-
Kalb county, namely, on the Stone Mountain public road, 2%
iniles east of Decatur, and in a cut on the Southern Railway, a
few hundred yards south of the trestle crossing South river. The
trap at the former locality occurs in the form of two small dikes,
apparently not over five or six feet in thickness. The rock occurs
in rounded, weathered boulders, scattered about the cultivated
fields at this point, indicating an extension of the dike to the
southward. The trap, here exposed, is a true oli vine-diabase. It
is a medium coarse-grained, dark-gray rock, whose weathered
surface reveals numerous crystals of plagioclase. Besides this
mineral, biotite and secondary hornblende are also easily rec-
ognized by the unaided eye. Examination under the micro-
scope, in thin section, reveals, in addition to the above minerals,

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the presence of aiigite, olivine and magnetite. The plagioclase is
seen as rather thick, stout, lath-shaped crystals, which are gen-
erally quite fresh and distinctly striated. The brown and green
hornblendes form narrow margins around the other ferro-magne-
sian minerals, from which they have been evidently derived.
The olivine is very abundant, and is much altered. The altered
product appears to consist largely of pale-green amphibole needles
or fibers, arranged more or less perpendicular to the surface of
the original mineral. The augite appears mostly as large, irreg-
ular plates, having distinct cleavage, and frequently having nu-
merous minute inclusions, with their longer axes parallel. The
magnetite and biotite occur only in small quantities. The rock,
here described, possesses all the qualities of a first-class road-

The other exposure of trap rock, spoken of above, is also in
the form of a small dike. It is associated with pyroxenites and
other ferro-magnesian rocks, which form a belt a mile or more in
width at the above named point. This rock differs from the true
diabase, in having a granitoid structure and a large quantity of
secondary hornblende present ; also, a small amount of enstatite
and hypersthene. It is a very difiicult rock to break ; and it
would make a durable and valuable material for road-surfacing.
A rock similar to the above, and probably a continuation of the
same dike, is to be seen on the McDonough road, about a quarter
of a mile south of South river. The exposure at this point has
a thickness of several feet, and is quite conspicuous in the cut of
the road, where the outcropping occurs in the form of rounded


Area, 126 square miles ; approximate road-mileage, 222 ; num-
ber of miles of graded road, o; number of miles of macadamized
road, o; amount of money annually raised for public-road pur-
poses, o. The roads are constructed and maintained mainly by

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Statute labor, and are worked, on an average, three days each

The County Ordinary, in speaking of the roads of Rockdale
county, says : *' We work our roads, under the old law, occasion-
ally expending small sums in blasting, making fills, etc. One of
the main difficulties in the way of road-construction in our county
is due to the way, in which the roads were originally laid out.
They frequently extend up and down hills without any regard
whatever to grades. Before any improvement of a permanent
nature is undertaken, many of the roadways should be re-
located." The road materials are granites, gneisses, schists and
probably trap. The granites are very abundant in the vicinity of
Conyers, where they are quarried for building purposes. They
are generally of fine grain, and are fairly well-suited for road-
construction. Trap rock is reported, in several localities ; but its
mode of occurrence and extent have not been investigated.

The county owns about 5,000 feet of .public bridges. All of
them are made of wood, and are generally in good state of repair.


Area, 389 square miles ; approximate road-mileage, 750 ; num-
ber of miles of graded road, 50 ; number of miles of macadamized
road, o ; amount of money annually raised for public-road purposes,
$9? 500- The roads are constructed and maintained by convict

Walton county is generally hilly. The soils are mostly clayey^
and are well suited for road-building. The streams are numerous.
The larger ones are spanned by well constructed wooden bridges,
one of which has been recently replaced by an iron bridge, costing
$800. The highways of Walton county are in fair condition.
They have been greatly improved under the present system of road-
working, which went into effect in August, 1895.

The roads of Walton county are now kept up entirely by con-
vict labor. The number of convicts employed varies from 25 to
30. They are under the direction of a superintendent, who is paid

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$47.50 per month. The cost of working each convict is placed at
$9.44 per month. This estimate includes the cost of guarding,
clothing, subsistence account, etc. The guards, three of whom are
regularly employed, receive $20 each per month.

The county levies a special road- tax oi 1^2 mills on the dollar,
of all taxable property. The amount, thus collected last year from
this source, was $4,500, making a total of $9,500, available for
highway improvement.

The road-wojking outfit belonging to the county consists of two
road-machines, several wheeled and drag scrapers, plows, wagons,
19 mules, etc.

The road-building materials are granites, gneisses, schists and
trap rock. The first three named varieties of rock are widely dis-
tributed, and can be had at almost any point in sufl5cient quanti-
ties for road-building purposes. A large exposure of gneiss may
be seen on Mr. W. H. Bush's property, near Winder.

Trap rock (oli vine-diabase) was examined at only one locality
in the county, namely, near Flat Rock Creek bridge, one mile
northwest of Jersey post-ofl5ce. This is a medium coarse-grained
rock. Plagioclase, augite and olivine are easily distinguished.
The color is a dark-gray with a slight tinge of brown, due appar-
ently to the presence of olivine together with its alteration prod-
uct. Thin sections under the microscope show the typical ophitic

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Online LibrarySamuel Washington McCallieA preliminary report on the roads and road-building materials of Georgia → online text (page 13 of 22)