Ellsworth American. [volume] (Ellsworth, Me.) 1855-current, 1894-11-15
GEOLOGY OF ROADS.
p"cnNcd stone Does Not Cement and
= Poor Material for Road Metal.

't'fHiN t'fl NtbHf tPtFN wv 'iAit ~ fAi''
j. Poor Material for Road Metal.
Practical information for the guild
ance Of all interested in the good roads
movement j. embodied in an important
report Of the United States geological
survey on the geology of the common
reads Of the Cnited States. prepared by
Geolagist y : Shaler The report out
lines the history Of American roads,
discusses the geological relations Of
common roads and the geological condi-
tion Of road materials and reviews the
sources of supply Of road stones.
With the invention Of maeadam, :
saws Professor Shaler. "a new path in
road construction was opened The
peculiar advantage arising from his dis
covery is that roads can be constructed
at relatively small expense as com.
pared with pavements made Of blocks,
and the work can - done IN many re-
gions where suitable paving blocks can
not be obtained. If a mass Of broken
stones is allowed to lie with the fras-
ments resting on each other, no evident
trace of concentration takes place, but If
the materials be repeatedly traversed by
heavy wheels or a roller Of great weight
then as soon as it is wet the cementa-
ton sets in
This fixing Of the bits Of stone to-
gether has been attributed 10 the inter
lacing Of their rough surfaces when they
are driven together The effect, how
ever. is due mainly to the fact that the
friction of bit on bit produces by the
grinding action sufficient amount Of
powdered rock TO form the required ce-
ment. The binding strength Of the Co.
ulent exists in some measure with all
the specs Of stone,
Ne decayed stone retains the capac-
itv Of cementatiun when powdered,
though in some few cases whore material
dargO a certain binding and no ordinary
fiiuty gravel> free from iron oxides can
be made t. form firm roadbed. PEI.
bleS. even though they eaunet be made
10 cement IL their natural state, VIII do
30 when broken into bits Thus the
macadam invention can be applied III
three way~-hreaking stone which Is
taken from the quarry, using stone bro
ken by natural processes and which i,
not decayed, and hy rebreaking pebble,
which in thor natural state cannot be
made 10 unite by the eementing proc
eSses
T he volcanic rocks, tie dyEe>toncs
and large crystalline masses and tine su-
perficial layas are the best fitted fer read
making, and Of these the material
known a. tasait Is much the best. TIE
lavas which have cooled in assures ar
stronger than those found on he earth
surface.
Almost as important as the character
Of - road sErtaee Is the grad, and *
perleHee shows that, except uuder 70.
uIiar eondj'iet.> 1t i vtry unprdftat.a
10 build roads having five feet Of fall IL
each loo feet # length. =
In general, the report concludes: Tn
greater part If the United states i
characterized by great seasonal yar;a-
lions and those climatic featu, - which
most affect the conditions Of carriage
roads There i prevallingly 81 !torI!a-
ton Of heavy rainfall and rr6traeted
drought. During rain periods the roads
are subjected TO a deep penetration Of
water and serious washiugS, In thu dry
season the upper surface becomes pow
derry, and these conditions make high
grade roads peculiarly necessary and
make their maintenance costly Phil
aGelphia Press