524 PRACTICE OF AGRICULTURE. Part III. 



if the stones are square and heavy, those small conduits may be built without mortar, 

 except at the ends. 



3364. In building tunnels or arches across a road in a flow bog, great pains must be taken 

 with the foundation, or the whole structure will inevitably sink : the building of those 

 should be deferred as long as possible, till the peat has subsided, and has obtained a 

 tolerable consistence ; then make an opening equal to the whole work, and sink it eigh- 

 teen inches below the intended bottom of the arch or gullet ; collect a quantity of black 

 thorn bushes, and tie them in faggots of the same size ; place these in regular courses 

 in the direction of the road, and lay across them a platform of strong plank three inches 

 tliick, the whole length and width of the intended mason work; on this build your 

 arch, and make an allowance in the height of the abutments for sinking. Wherever walls 

 are necessary to support banks, and prevent their crumbling down upon the road, if 

 large even stones can be procured, they will not require any mortar ; when mortar is 

 used, there ought to be a great many apertures in the work to give vent to the water, 

 otherwise the pent-up moisture from behind will push out the wall. In many cases, 

 where embankments can be made of earth and sods, they are to be preferred to masonry, 

 which is extremely expensive at the commencement, and very perishable for mortar 

 soon loses its cementing quality, when exposed alternately to frost and damp. 



3365. Draining the site of a road on ajiow-bog, according to Clarke, is a tedious oper- 

 ation, and often requires some years. A single drain at each side will not be sufficient, 

 as the water from the adjacent moss would fill it up as fast as it was made. Lay out the 

 road here sixty feet wide, which will allow for the banks when the whole shall be finished; 

 make a drain at each side six feet wide, and at a distance of fifteen or twenty feet more, 

 parallel drains of the same width. If the interval between the parallel drains is after- 

 wards cut away regularly for fuel, it will tend still to the condensation of the moss. 



3366. Open drains in the case of ground liable to sink, or to moulder down by frost, 

 ought to be made very much sloped on tlie sides, especially the side next the road, other- 

 wise, after repeated scouring out, the road will be found to have sunk at the sides; a 

 very common case, and highly injurious in the case of narrow roads. Whenever this 

 tendency to sink is observed, it should be made up by the scrapings of the road, or by 

 other materials. Roads made over bogs, and artificial mounds, are particularly liable to sink 

 at the sides, which should be immediately counteracted to prevent the bad consequences. 



3367. Fences along the sides of roads are essential in all enclosed countries ; and all 

 engineers and road-makers agree, that they should never be allowed to rise of a greater 

 height than what is necessary for a fence. To give free admission to the sun and air by 

 keeping the fences low. Marshal considers as providing an inexpensive, yet most accurate 

 method of cleaning roads, incomparably more so than washing or scraping. The legis- 

 lature, Edgeworth observes, has limited, in several instances, the height of hedges to 

 five feet ; but this limitation is neglected or evaded. Even were it strictly adhered to, 

 it would not be sufficient for narrow roads ; the hedges would be still too high, for it is 

 the sweeping power of the wind, which carries off dust in dry weather, and which takes 

 up moisture in wet. In fact, roads become dry by evaporation ; and when they are ex- 

 posed to the sun and wind, the effect of heat and ventilation are more powerful than any 

 surface drainage that could be accomplished. 



3368. Walker observes, that the advantage of having the hedge next the road, consists 

 in its greater safety to the traveller, particularly if a ditch of any considerable depth is 

 necessary, and in the hedge being supported in its growth from the ground under the 

 road, without drawing upon the farmer's side of the ditch. 



3369. The fences, Telford observes, form a very material and important subject, with 

 regard to the perfection of roads ; they should in no instance be more than five feet in 

 height above the centre of the road, and all trees which stand within twenty yards from 

 the centre of it ought to be removed. I am sure that twenty per cent, of the expense of 

 improving and repairing roads is incurred by the improper state of the fences and trees 

 along the sides of it, on the sunny side more particularly ; this must be evident to any 

 person who will notice the state of a road which is much shaded t^ high fences and trees, 

 compared to the other parts of the road which are exposed to the sun and air. My 

 observations, with regard to fences and trees, apply when the road is on the same level as 

 the adjacent fields ; but in many cases, on the most frequented roads of England, more 

 stuff has been removed from time to time than was put on ; the surface of the road is con- 

 sequently sunk into a trough or channel from three to six feet below the surface of the 

 fields on each sides ; here all attempts at drainage, or even common repairs, seem to be 

 quite out of the question ; and by much the most judicious and economical mode, will be 

 to remove the whole road into the field which is on the sunny side of it. {^Exam. before 

 the House of Commons, ^-c.) 



3370. In the junction of roads, whether of a bye-road with a principal road, or two 

 bye or principal roads, their respective levels ought, if possible, to be the same, and the 

 materials ought to be rather broader than usual at the point of turning. In like manner 



