MEANS OF COMMUNICATION. 3 
inches in depth, of flat stones (statwmen) laid in mortar and breaking joints, 
which serves as a support for the second stratum of 8-10 inches, composed 
of concrete (rudus) or small pebbles cast in cement. The third layer con- 
sists of a mass of lime and brick-dust (#wcleus), on which finally was placed 
a stratum of gravel or a stone pavement (swamum dorsum). In this way 
the body of the road was something over three feet in depth. Besides these 
roads they had others of less importance, consisting of two gravel-ways 
twenty feet in width. 
In the middle ages the Roman roads were suffered to fall into decay, and 
no new ones were constructed except in France by Queen Brunehild, for 
which reason causéways are even now called chemins brunehauds in Bel- 
gium. In modern times causeways were first built in Holland, and 
subsequently in Spain, England, Germany, and France. 
A. Streets in Cities. 
Streets in cities are paved with stones almost without exception, and only 
in some cities the streets in the suburbs are made in the manner of cause- 
ways as we shall describe them below. | 
The paving of streets may be done in two ways; that most commonly in 
use is represented on pl.1, jig.5. ‘There are others, however, constructed in 
the manner shown in jig. 38. Every street should have side-walks along the 
houses (jigs. 3, 4, 5, 6) from three to eight feet wide, covered with flags of 
granite, or paved with bricks; the latter, however, should only be used 
where nothing better can be obtained. Some years ago asphaltum was very 
much advocated ; it was mixed with very fine gravel and spread in a semi- 
liquid state over the side-walks, when after cooling it presented a smooth 
surface similar to granite. The idea was soon given up, however, as the 
wear of the asphaltum was very great, and it became soft in very warm 
weather. 
The carriage-way of the street should be elevated in the centre (jig. 3) 
and slightly arched, so as to turn the water to both sides, where it runs off 
more readily in gutters (a, fig. 3, and g, fig. 5), which must have a longitudinal 
descent. In cities provided with sewers which run along under ground 
usually in the middle of the streets, and carry off the rubbish from the 
houses as well as the water from the streets, the latter may be much 
less arched ; the gutters are in that case provided with conduits covered 
with grating, through which the water enters the sewers; these also 
have openings through which they may be entered from the street and 
cleaned. ! 
In places where the soil is firm and the seasons generally dry, the pave- 
ment itself may be made in the manner shown in pl. 1, jig. 3 being a 
section, and jig. 4 a ground-plan. Here the tracks of the wheels only, ec 
( fig. 3), and EF (fig. 4), are laid with closely fitted stones, and the spaces 
b, d, and 6 (jig. 3) are covered with well-rammed gravel. In most cases, 
however, the pavements are made as shown in jigs. 5 and 6, where the 
whole street is paved with round stones (pebbles) fitted together as closely 
as possible. The wheel-tracks should in any case be laid with flat stones, 
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