397 
PARK AND CEMETERY . 
ing one inch in thickness) will cost 
about 15 cents, or say 20 cents as an 
outside figure. An extended experience 
of the w'riter during this season in this 
sort of work indicates that 17 % cents 
is a safe average figure. In this condi- 
tion, the road surface is comparatively 
solid and imyielding, but not in a con- 
dition to carry any considerable traffic 
without some sort of paving surface 
over it. 
A 5-inch concrete layer would cost 
about 60 cents per square yard, and to 
remove the. macadam and prepare for 
the concrete, 15 cents per square yard. 
The concrete would probably have some 
more stability and be safer to use than 
the macadam if it was intended to lay 
a brick or block pavement, or a sheet 
pavement of a kind that depended on 
the base for stability against shifting. 
The use of concrete, however, would 
mean throwing away macadam worth 
60 cents, and an additional expenditure 
of 75 cents per square yard. 
The obvious thing to do would be 
to use a paving material adapted to 
utilize the existing macadam base, and 
one that can be varied in construction 
somewhat, according to the needs of the 
traffic. As stated above, a brick or 
block pavement would not be an ideal 
one to use, as each individual block must 
in a measure find its own bed and carry 
practically all the weight imposed on it. 
Brick, creosoted Itlock or granite, be- 
sides having other objections for use on 
such roadways as we are discussing, 
would not be flexible in cost to meet 
varying conditions of traffic. A stand- 
ard construction with standard size 
blocks would have to be adopted, which 
would probably be suited to an en- 
tirely different traffic from that under 
consideration. 
The obvious thing to do would be to 
choose some form of sheet pavement, 
preferably a bituminous composition, 
that would assist in bonding and bind- 
ing the old macadam in place, adjust 
itself to slight inequalities of support 
and be more or less variable in thick- 
ness (and consequently variable in cost) 
according to the needs of the traffic. 
The more common form of sheet as- 
phalt pavements answers these require- 
ments to some e.xtent, but the objections 
to it are as follows: It must be made 
comparatively thick, say three inches, to 
conform to accepted standards ; its cost 
is dependent on its thickness, but not in 
direct ratio thereto ; it is more or less 
dependent on the base for its stability 
and consequently not safe to use on such 
a base as we are describing; it has a 
smooth, sheet-like surface more or less 
slippery, and not desirable in appear- 
ance for boulevards and driveways with 
rural surroundings. 
The ideal pavement for such condi- 
tions would be a bituminous composi- 
tion with crushed stone as the principal 
mineral ingredient. The stone in the 
body and surface of the pavement would 
bond well into the macadam, afford a 
good foothold and present a desirable, 
grainy surface to the eye similar to 
well built macadam. The size of the 
stone should he regulated by the thick- 
ness of the bituminous layer desired 
and that regulated by the amount of 
traffic to be expected. The bitumen 
should he soft enough at all seasons to 
make an elastic and noiseless pavement, 
and yet of sufficient stability and con- 
stancv under extremes of temperature 
to hold the mineral aggregate firmly in 
place. If the bitumen becomes very 
soft under the summer heat it may act 
as a lubricant between the particles of 
stone instead of a stable binder. 
Several forms of bituminous pave- 
ment, such as are known as tar ma- 
cadam, bitulithic, asphalt macadam and 
asphaltic concrete, have at least some 
of the qualities named above. By tar 
macadam and asphalt macadam are 
meant pavement surfaces produced by 
the pouring, i)enetration or grouting- 
method. To accomplish the best re- 
sults by this method, there should be 
a layer of clean, coarse stone spread 
on top of the macadam liase described 
above, and lightly rolled just enough to 
level the stone off and set it in posi- 
tion. The size of the stone should be 
THE PORTABLE MIXING PLANT AT WORK. 
Showing Operation of Feeding. 
PORTABLE ASPHALT MIXING PLANT ON PARK DRIVE. 
Gasoline Traction Engine Belted Up Ready for Work. 
