The Havre herald. [volume] (Havre, Mont.) 1904-1908, 1907-01-04

SPREADING CHERP MATERIAL ON A ROAD.
terially in their origin Cherts occur
usually in chalk and limestone forma- |
tons and are generally believed to be !
formed by a chemical precipitation |
from sea water. Novaculites. on the |
other hand. are thought to be true sed-
imentary rocks, having been formed by |
deposits Of very fine material-sllt ana |
sand--in sea water and subsequently |
solidificd The useful qualities of no
vaculitcs as oilstones for sharpening |
fine tools are well known and are due !
to the hardness and SlnoothnesS Of this |
rock.
In order that road may bind WELL
its surface must be composed Of fine
particles Of suitable r0cE which form
the bond. If these particles are blown
or wsshed away they must be replaced,
or the bond will be broken and the
road will ravel. When roads arc sur
faced with limestone Or ebert COM
parativeIy light traffic can be depend
ed upon to supply enough binder 10
keep tue road from raVeling. For this
reason these materials are better adapt
ed to light traffic than harder and
tougher rocks.
When bank cherts are first spread
upon the road they are sometimes soft
and brittle and apparently almost use
less as Il road material, but when
the materials are exposed to the action
of traffic and the elements the surface
n
Cherts and noyaculites are invariably
found in sedimentary formations. The
material is also found sometimes COM
pletely covering the ground, sometimes
in the beds of streams and narrow val
legs, where it has been deposited by
the action of the water, and again Ia
banks and pockets on hill and noun
tain sides Cherts are usually found
in nodular masses, but like novacu-
lites, may occur in angular fragments.
varying in size from about one to six
inches.
Where these materials are found ia
banks or the beds Of streams they are
commonly called gravel. Creek gravel,
formed from ebert or novaculite, is
usually of uniform size and compara-
lively clean, while the bank gravel
often contains earthly matter and tine
particles of the same material. The
creek gravel usually wears the best.
but it does not bind so readily or form
as smooth a surface as the bank de-
posts. Where both creek and bank
gravel is available good results can
be obtained by using the former for
foundation and the latter for wearing
or binder course. The writer used
this method at Florence, Ala. with
marked success.
Where the material is plentiful and
where good quality Of bank gravel
is available for a binder it is unneces-
sary to go to the trouble and expense
of cutting out subgrade or to pre-
pare earth shoulders, as is done fol-
: regular macadam. II the shoulders
} are dispensed with, however, it is alb
1 solutely essential that the surface
l course contain a sufficient quantity Of
1 good binding material; otherwise the
e bond will soon be broken, the materia
: will spread, and much Of it will even
a tually be forced or washed into tn
o side bitches. The roadbed should o
|. course be shaped with road machine
J. before the material is placed and giyel
e a slight crown Of from three-eighths t.
one-half of an inch to the foot iron
0 the center to the sides. The founda
It ton should then be rolled and the mate
It rial for the first course spread in tW
f. layers and rolled and sprinkled in tn
s. usual manner. The spreading of tn
II material can be accomplished by tn
II use OF road machine, provided th
IS gravel is not too large. The tot;
" depth OF material may vary from fot
i to nine inches at the center, as so
is and traffic may require, and Gradua
if " diminish in thickness to what
is commonly. called Il feather edge ;
IF the sides. If the most approved met
% cd is followed, shoulders should be pr
"a vided to hold the material in plac
TT The material should then be spread
he uniform depth from the center
aiIaS