Wiirtemberg 



431 



and i meter long, piled one above the other. These dimensions 

 are varied somewhat on different routes. Fig. 153 shows the end 

 section of such a trough, with the method of joining two lengths. 

 Fig. 154 shows a complete conduit for thirty cables, composed of 

 six such troughs superimposed. A trench is dug, and lined at 

 the bottom with concrete which is slightly raised along the 

 middle so as to afford a hold to the sides of the first inverted 

 trough. Subsequent troughs are added till the desired capacity 

 is attained. When laid under the footpath, the trench is then filled 



- :s.\rv ~ 



FIG. 153 



in with soil, and a layer of concrete added immediately below the 

 flags. This construction is shown in the left-hand half of fig. 154. 

 When laid under the roadway, as in the right-hand half of the 

 figure, injury from the weight of the traffic has to be provided 

 against, and the trench itself is filled up with concrete, between 

 which and the paving stones a layer of sand or gravel intervenes. 

 When a conduit of very large capacity is required, two tiers of 

 troughs are laid side by side. Fig. 155 shows the manholes and 

 draw-boxes, in plan and section, as arranged for a conduit of two 



