Vilas County news. [volume] (Eagle River, Vilas County, Wis.) 1896-1927, 1901-04-01

is an article Dy III. II. H. AooAAAO1'
assistant superintendent of the Wis
consin geological survey, on tar
macadam, a theme that has been dis
cused in these columns heretofore.
This kind of a pavement, says DR..
Buckley, is. really a cross between an
asphalt pavement and macadam. III
the construction of asphalt pave
ment the principal constituent OF the
wearing surface is sharp, angular
sand and asphalt. In the wearing
surface of the tar macadam the
principal material is quartzite or
hard granite rock The tar is used
simply as a bonding constituent and
is in no way intended as part OF the
wearing surface of the pavement.
The wearing capacity of the tar
macadam is measured entirely by the
hardness and strength of the rock out
of which it is composed; only sui
ficient tar being used to unite the
fragments into solid uniform mass
Up to the present time these pave
ments have been built more extensive
ly in Canada than in this country
Toronto, Ottawa, and London, in the
province of Ontario, have been build
ing pavements Of this character for
several years. In Fredonia and Al
rora New York, tar macadam pave
ments have also been constructed.
The following specifications for tar
macadam roadways as constructed in
London, Ontario were furnished by
Ormsby Graydon, city engineer of
London:
HThe earth should be exceyated and
blocks removed to a dept of twelve
inches below the line of finished
grade. This foundation should be
thoroughly wetted and rolled with
heavy horse rollers. Upon this
foundation should be placed six inches
of clean, coarse gravel the gravel to
conform with the cross section and
finished grade of the street, and
should be wetted and rolled with a
steam roller. Upon the foundation of
granite when thoroughly rolled should
then be placed three inches of coarse
grained, hard crushed stone capable
of passing through a / u inch ring, 20
per pent of which being fine crushed
and capable of passing through a 1 u
inch ring. Inc crushed stone should
be heated on a steel platform in pans
to 120 degrees and on this heated
crushed stone, tar composition should
be poured until thoroughly covered
the tar to be heated to the boiling
point, 212 degrees, and the pitch TO
about 240 degrees, the whole to be
thoroughly mixed in the same manner
as concrete is mixed. After thorough
Iy mixing it should be hauled on the
street and graded evenly to the re-
quired depth then rolled with steam
roller. When Thoroughly rolled, a
second course two inches in depth OF
crushed stone capable of passing
through a ~ and l inch ring, re-
SpectiVely, must be mixed in the same
manner as regards heat, mixture, ap-
plication, ETC., but need only be rolled
with the hand roller Upon this
second course must then be spread
the finishing coat one inch in thick
ness, composed of az thorough mixture
of sand, pitch, and tar; sand to be
heated to at least T20 degrees. This
coat must then De applied while hot
and spread evenly to the proper
thickness, and rolled with the hand
roller. After which the whole pave
nent should be thoroughly rolled with
a >steam roller, and sanded with dry
sand one-half inch in depth Tar is
to be heated PIP degrees and pitch
$40 degrees and properly mixed at a
rate of ten gallons of tar to one gal
lon Of pitch per cubic yard of crushed
stone; eleven gallons of tar to one of
pitch per cubic yard of top coat
Stone must be good and hard No
limestone will be allowed. Coal gas
should be clean, containing no water
gas tar. Pitch should also be the
best of it's kind, manufactured from
pure coal gas tar
3. B. Wingate, city engineer of
Hamilton, also furnishes specifica-
tions for tar macadam roadways as
constructed in that city The follow
ing is copy:
"All earth or other material above
as to conform to the level of the sub
grade which will be ten inches below
the finished surfare of the roadway;
and should the sub-grade be above the
level of the natural ground, then
earth must be deposited until the
level of the sub-grade is reached.
The sub-grade must be shaped to the
profile and cross section which will be
furnished by the city engineer. After
the sub-grade has been formed to the
proper Gambler of the road, generally
12 inch per foot or six inches for q
foot roadway, to be thoroughly rolled
with the steam roller, and if by this
means soft spots are revealed, they
must be flied with good solid material.
The first six inches of stone must be
made in the ordinary way for a
macadam or telford roadway thor
Oughly rolled. If SO required, it NAV
he made of hard hrOlxap c+0v,o e.,