The Mankato free press. [volume] (Mankato, Blue Earth County, Minn.) 1879-1924, 1912-05-03

is mixed with river or creek gravel the
result is not likely to be as satisfactory
as that obtained by the use Of pit gray
el. Pit gravel frequently contains too
much clay OF earthly matter. while river
gravel may have too much sand. In
such cases 1t is sometimes advisable to
screen the gravel SO as to eliminate the
material which is too fine or that which
is too coarse. The screen should be
similar to that which is used in pre-
pairing material for macadam road
In the handling of the gravel care
should be exercised not to separate the
binding material from it, nor should
this binding material be allowed to
settle to the bottom i'll spreading the
material over the road surface 1t
will often be found advisable to spread
a thin layer of such binding material
over the surface after the material has
been distributed and rolled, and after
this the surface should be sprinkled
and rolled again or else rolled while
still damp from the rains.
large part Of the gravel found in
the Atlantic coastal plane is sufficient
ly fine and uniform to render unneces-
sary any asserting for road building
purposes, but wheE the gravel, eSpe-
cialIy that which Is to constitute the
surface layer. contains large pebbles
these should be removed and either
thrown aside or else raked into the
foundation or recrushed. At least GO
per cent by weight of the gravel should
be pebbles above one-eighth inch in
size, and there should he no pebbles in
the bottom layer that will not pass
through two and half or three inch
ring, and in the top layer there should
be no pebbles which will not pass
through a one aud one half inch ring.
Not over 20 per cent of the mass
should he clay, and this should be uni
formIy mixed and should contain no
large Jumps. Ten or 10 per cent Of clay
produces better results than 20 per cent.
If the foundation or roadbed is loose
it should be carefully rolled. 1t is
quite as important to have a solid
foundation for gravel road as for a
macadam road Gravel will compact
to about 80 per cent Of its depth, loose
measure, provided earth shoulders are
placed on both sides of the road to
prevent the wasting away Of the
gravel on the sides. If gravel is abun-
dant, however, these shoulders may be
built of gravel instead of with earth,
or the road may be surfaced with
gravel from shoulder to shoulder. If
the compacted depth of the gravel
road is to be eight inches and the
width twelve feet it will take about
$3.50 cubic yards of gravel to the mile,
and it is best to make the first layer
about six inches in depth, loose meas
ure, and the second layer about four
inches in depth, loose measure.
Gravel should not be dumped direct
ly On the road, as this will usually re-
suit in a rough, uneven surface. If
specially devised spreading wagons
are not used the gravel should be
dumped on boards and spread from
them ON to the road.
The gravel should be placed on the
road commencing at the end nearest
the gravel pit. in order that the teams
will aid in packing the material. A
spike or tooth harrow may be used to
advantage in spreading the material,
but if the gravel contains only small
amount of binding material the har-
row should not be used, as it will have
the effect of bringing the larger peb-
bles to the surface and shaking the
binding material to the bottom.
Each layer Of gravel should be rolled
separately. The rolling should begin
at the sides and continue toward the
center until the surface is thoroughly
compacted The surface layer should