48 BOARD OF AGRICULTURE. 



right angles to the line of draught, the lahor of the horse and the 

 wear of wheels is very greatly increased. The evil of too great 

 convexity is manifold, and a vastly better form is that of two 

 inclined planes meeting at the centre, with the angle of junction 

 at the top slightly rounded by a curve. Of course the exact 

 inclination will depend much on the character of the surface 

 and on the width of the road. A very rough and bad surface 

 will require a greater incline than a hard smooth face, but no 

 road should ever be allowed to be so rough as to require a 

 transverse inclination greater than one in twenty, which for a 

 road-bed twenty feet wide would make the centre six inches 

 higher than the sides. With a broken stone or a hard unyield- 

 ing surface, a proper medium of one in twenty-four is adopted, 

 or half an inch to a foot. Telford, the most successful and 

 noted road-builder of England, adopted one in thirty, or six 

 inches curve in a road thirty feet wide, and MacAd^m fixed 

 upon one in thirty-six, and sometimes as slight as one in sixty, 

 or only three inches crown in a thirty feet road. 



The transverse slope should increase with the longitudinal 

 inclination, and should always a little exceed it in order to pre- 

 vent water from running down the length of the road to gully it 

 out, but it must be apparent that no practicable amount of 

 crowning or convexity would serve to carry the water from the 

 slightest rut, not even if it were only an inch deep. And hence 

 MacAdam testified before a committee of Parliament, saying: 

 " I consider a road should be as fiat as possible with regard to 

 allowing the water to run off it at all. I have generally made 

 roads three inches higher in the centre than at the sides, when 

 they are eighteen feet wide." Now a dirt or even a gravel road 

 may require a little greater inclination than the solid surface of 

 broken stone, but if the road is so neglected as to have a soft or 

 loamy surface, no amount of convexity will shed the water, and 

 a very convex surface will invariably hold the more water. 



It should be constantly borne in mind that any convexity 

 at all is a necessary evil, and that the less it can be and accom- 

 plish its ol)ject the better for the travel. 



Analogous to this great fault is the practice, often seen on a 

 wide road and through a village street, of dumping down along 

 the centre of the highway a kind of winrow of material, whether 

 loam or gravel, eight or ten feet wide and from six inches to a 



