Evening star. [volume] (Washington, D.C.) 1854-1972, 1913-02-02

much improved by the use of any rock,
this regard for economy is not to be en-
tirely deprecated. At the same time, as
a careless selection leads TO costly ana
inferior results. too much care cannot De
used in selecting the proper material
when good roads are desired at the low
est cost. When macadam ROADS are nfst
introduced into a district they are AT
worst so far superior to the old eartn
roads that the question is rarely asked
whether. if another material had been
used better roads would not nave been
obtained. and this at smaller cost
When mistakes are made they are not
generally discovered until much time and
money have been expended on inferior
roads. Such errors can in a great measure
III. avoided if rea SOnabie care Is taken IN
the selection of d suitable material. 10
select a material in a haphaZard way,
without considering the needs of the par
ticular road on which it is to be used,
is not unlike an i'll person taking the
nearest medicine at hand without reler-
ence to the nature of the malady or the
properties of the drug IL road Is pad
the exact trouble must first be ascertain
cd before the proper remedy can De APP
piled II the surface OF a macadan ROAD
continues TO be too muddy or dusty after
the necessary drainage precautions nave
been followed. then the rock OF which 1t
is constructed lacks sufficient hardness
or toughness to meet the trafnc TO Whlch
II is subjected. If. on the contrary, the
fine binding material of the surface is
carried off by wind and rain and Is not
replaced by the wear of the coarser rag
ments the surface stones Will soon loosen
and allow water TO make its way freely
IN the foundation and bring about the
of the road. Such conditions
are brought about by an excess OF hard-
ness or toughneSS OF the rock lor the
traffic. Under all conditions rock Oh
high cementing value Is desirable; for
other things being equal. sucn rock
better resists the wear of trafhc ana the
action of wind and rain. This subject
however, Will be referred to again.
Learning Value of Rock.
Until comparatively recent years but
little was known Of the relative values
If the different varieties of rock as road
material. and good results were obtained
more bv chance and general observation
than through any special knowledge OF
the subject These conditions, however,
do not obtain at present, for the subject
has received a great deal OF careful
study. and a fairly accurate estimate can
be made of the fitness of a rock Tor any
conditions of climate and traffic.
In road building the attempt should be
made TO get a perfectly smooth surface,
not too hard too slippery or too noisy,
and as free as possible from mud ana
dust and these results are 10 be at
tanned and maintained as cheaply as pos
sible Such results. however. can only
De had by selecting the material ana
methods of construction best suited TO
the conditions.
In selecting a road material 1t is well
10 consider the agencies of destruction to
roads that have TO be met. Among the
most important are the wearing action
OF wheels and horses feet. frost rain
and wind. To find materials that can
best withstand these agencies under all