TRANSPORTATION ON LAND BY VEHICLES:— THE ROADS 51 



Open pole cross runs consist of 1, 2, or 3 poles, framing an open ditch running either diagonally or 

 square across the road. Open cross runs constructed of boards are rarely found. Open cross runs paved 

 with stones put on edge and having a pitch across the road of 5 to 10 per cent are very effective. They 

 are the most reliable means of open cross drainage. They are, however, bad impediments to traffic, unless 

 they are run diagonally with the stones thoroughly driven into the ground. 



Cross runs consisting of cross ditches filled with stones placed loosely on a solid basis, or filled 

 with poles or faggots are permissible only where the soil is fairly permeable and where the grade of the 

 road is not too steep. 



(b) Covered cross runs. Covered cross runs are either culverts, usually consisting of drain pipes 

 imbedded in the soil, or causeways constructed in dry masonry, or small bridges. 



The simplest culvert is a wooden box made of four pieces of 2 " ■, 10" plank. This box, however, is 

 apt to get stopped up; it rots quickly in the ground unless it be made of chestnut, white oak, cypress, &c. 



Stone causeways are advisable where the underlying rock is stratified (sandstone, schist, slate) so 

 that large flat stones can be cheaply obtained for covering purposes. The span should not be over 3 feet. 



Causeways constructed as bridges consist of 2 or 4 mud sills placed with the big end towards the 

 valley, three stringers 6 to 12 feet long and a covering of boards or half-splits. 



In certain sections of Pennsylvania, corrugated iron culvert pipes (18 cents a foot for 8-inch pipe) have 

 been found a splendid substitute for open thank-you-m'ams. The pipe is laid into the cross run, loose 

 rock is packed tightly against it so as to form a protective wall, and the whole is covered with a surface 

 dressing of small gravelly material. 



The cheapest drain pipe is the cement drain pipe constructed at the place of using with the help 

 of a turned wooden cylinder and a wooden box. 



At the outlet of cross runs, the slope of the road might be protected from washing by stone walls 

 or pole chutes. 



Causeways and culverts do not intercept the ruts. It is necessary to force the water to the right 

 and left from the road bed either by side runs or by ties (as in railroads), or by occasional pieces of 

 heavily crowned pavement. On slate rock it is often possible to give the entire roadbed a pitch of not to 

 exceed 10 per cent across the road. 



The expenses of culverts consist of the following: — 



1. Digging or blasting of ground and rock. 



2. Hauling of timber, stones, and pipes. 



3. Construction of walls, pavement, covering. 



One workman lays in one day 1*3 cubic yards of dry stone walls, for which are required 17 stacked 

 cubic yards of rock, there being some loss. 



A good workman puts up in one day from 24 to 36 square (not cubic) yards of rough rock pavement. 



The following "rule" relative to distance between and to number of cross runs might be kept in 



mind: — The average distance between successive cross runs should be paces, when p is the percentage 



of grade of road. The number of cross runs per mile should be 10 p. 



(1) SUPERSTRUCTURES STRENGTHENING THE TRAVELLED SURFACE OF A ROAD. Water 

 and traffic destroy the road. A strong road surface is required to prevent or to check destruction. This 

 surface may consist of:- 



A dirt cover (dirt road, sand-clay- roads). 



A wooden cover (corduroy, plank roads, &c.). 



A steel cover (railroads). 



A stone cover (Macadam roads, &c.). 



I. Dirt cover. Dry dirt roads are as good as stone roads. Wet weather, however, causes the "melting" 

 of clay and lime. Quartz sand is, indeed, invaluable, and its "affinity" to water is small. Sand, however. 



