526 PRACTICE OF AGRICULTURE. Part III. 



cover the whole bottom of the road with vegetable soil, in cases where the natural shape 

 of the ground admits; he would not remove the ori<jinal surface ; and where there are 

 inequalities he would fill them up with vegetable soil, so as to cut off all connection 

 with clay. 



3378. In forming the basis of a road on a jlovo bog, Clarke directs to strip the heathy 

 sods (tussocks) off the whole surface of the side-drains, and place them with the heath 

 uppermost on the space intended for the road ; or if a sufficiency of brushwood or furze 

 can be procured, it will answer still better ; proceed to let off the water at the lowest ends 

 of the drains, leaving an open channel in the middle of each ; after the water has run off 

 for some time, so as to allow the moss to become somewhat finer, throw off another spit ; 

 and repeat this operation month after month, and year after year, till the space for the 

 road becomes compact and dry ; and be sure to keep it in that state by cleaning the drains 

 frequently ; there should be eight or ten inches of tough clay laid over the tussocks or 

 brushwood, which will be greatly the better to be consolidated by rollers ; this part of the 

 road may be left rather higher in the centre than the other parts, to allow for settling. 

 There is no situation where it is more difficult to make a good road than through a flow 

 bog, but if once made well, it is the most permanent of all roads, and from its elasticity, 

 the most easy to horses. 



3379. In forming the basis if a road on thin moor, the whole of the peat should be re- 

 moved from the space on which the road is to be made ; for, if allowed to remain between 

 the hard subsoil and the small stones, the weight of carriages would press down the latter, 

 force up the black peat through them, and totally spoil the road ; this happens only 

 where there is a thin, soft, peaty stratum between two hard bodies, for in deep bog, the elas- 

 ticity of the foundation yields to the superficial pressure, and contributes to the durability 

 of the materials ; after this has been so removed, the surface, when formed and drained, 

 will be ready for the road materials. 



3380. Informing the base or metal bed, Paterson observes, " it is common to cut it to 

 the exact breadth and depth of the metals, and to make it quite flat in the bottom, or level 

 from the one side of the metals to the other. Supposing this metal-bed to be formed 

 fourteen feet broad, and nine inches deep, on a breadth of fourteen feet, the metals 

 would require to be about three inches higher in the middle than on the sides. In this 

 case then, they would be nine inches deep on the sides, and twelve on the middle ; and as 

 it is evident that the middle of the road, where the metals are deepest, is not subjected to 

 so much fatigue and waste from the tread of the horses' feet, as that nearer the sides is 

 from the grinding of the wheels, this is, therefore, a waste of metals on the middle of the* 

 road. But this is not the greatest evil of which I complain. The metal -bed being cut 

 into the solid ground, and^a^ in the middle, and having the earth on each side about 

 nine inches higher than it, this, upon any other ground than that of dry sand or gravel, 

 forms a bed for retaining the water, as well as for holding the metals, which often deluges 

 the middle of the road with mud or gutters, when it might be prevented. I would 

 therefore propose, that a metal-bed of fourteen feet broad should, instead of being level, 

 have a rise in the middle of at least four inches, which will make a declivity from the middle 

 to each side of nearly two inches in the yard. Then supposing the surface of the metals 

 to have the same shape as mentioned above, viz. three inches higher on the middle than 

 on the edges, the metals on the sides will be the same depth as formerly mentioned, 

 namely, nine inches ; but instead of twelve inches on the middle, they will then only be 

 seven inches deep, which makes a saving of five inches. This saving of five inches on the 

 middle, or two inches and a half on the whole breadth of the metals, is very considerable ; 

 but this is not the only benefit arising from this mode of procedure. The metal-bed having 

 a slope from the middle to each side of the road, so far from retaining the water, runs it 

 off from the middle ; and this will be of more service in keeping the road in good order 

 ever afterwards, than if you were to put three or four inches more of additional depth to 

 the metals on the common plan. This appears to me to carry so much of common sense 

 on the face of it, that I am surprised it has not ere long this time been generally adopted." 

 Here Paterson seems to infer that water may, or rather does, penetrate the stratum of 

 metal to the base, which, in properly made roads will at least, not often be the case. The 

 argument of a saving in materials is quite sufficient to justify him and Telford in adopting 

 the elliptical form for a basis. 



3381. A soft base is always preferred by M'Adam, who drains effectually and puts no 

 intervening material between the metals and the earth, even if it were a bog, " provided 

 it admitted a man to walk over it." (^Examination, ^c. 1819.) The Somersetshire 

 morass is so extremely soft, he says, " that when you ride in a carriage along the road, 

 you see the water tremble in the ditches on each side ; and after there has been a slight 

 frost, the vibration of the water from the carriage on the road, will be so great as to break 

 the young ice. I never use large stones on the bottom of a road ; I would not put a 

 large stone in any part of it, nor faggots, nor any material larger than will weigh six 

 pupces. If a road be made smooth and solid, it will be one mass, and the effect of the 



