ON THE CONSTRUCTION OF ROADS. 133 



and we must take such roads where we find them ; we cannot make 

 them. 



A clay road, although good for certain short seasons, is usually 

 intolerably dusty in summer and soft and muddy in winter ; conse- 

 quently objectionable. 



There are also certain swampy, soft soils, over which road building 

 is attended with great difficulties. On the other hand, a road through 

 a gravely soil, if well drained, generally is sufficiently good; and there 

 are certain hard clay slates and shales which make roads of the very 

 best character. When, therefore, we are called upon to improve a road 

 by covering it with some material, we may select gravel, slate, cinder, 

 charcoal, or broken stone. 



Gravel for this purpose should be neither very clean nor too dirty ; if 

 the former, it will not pack or bind together, but will remain loose and 

 incoherent ; if the latter, it will not drain properly, and will be affected 

 •by moisture and frost. ■ The stone should be angular, rather than 

 round. Slate, furnace cinder, and charcoal can only be procured in 

 certain localities, and the last is objectionable from the black dust which 

 arises from it ; they are all, however, admirable materials, and can be 

 often used with great advantage. 



Broken stone, which can be had in nearly all localities, is, however, 

 the material most commonly in use. It should be hard, so that the 

 angles of the fragments should not be ground off by the wheels ; the 

 close-grained limestones and most of the porphyritic rocks being well 

 adapted to the purpose. Any stone which is disintegrated by exposure 

 to the weather, should be carefully avoided. The stone should be broken 

 into pieces of such a size that they will pass through a ring two and a 

 half inches in diameter, and as nearly of the same dimensions as pos- 

 sible, uniformity being of great importance. 



The road having been properly graded, with a slope to both sides as 

 before described, the broken stone must be laid upon it to a depth of 

 from ten to twenty inches, watered a little if the weather is dry, and 

 the traffic of the road permitted to come upon it. It should be kept 

 clean, the practice of scattering earth over the surface being especially 

 pernicious, since it prevents the stones from binding well together. A 

 better and quicker method of causing the stones to bind together is to 

 roll the road witli a heavy iron roller, but of course it is more trouble- 

 some and expensive than merely permitting the travel to do it. 



In the neighborhood of cities especially, where there is much pleasure 

 travel, it may sometimes be a good plan to stone the middle of the road 

 only for a width of about sixteen feet, and leave a soft summer road of 

 clay on each side. 



The preparation of the road bed to receive this coating of broken 

 stone, has been the subject of discussion between two eminent road- 

 makers in England — Telford and McAdam — and opinion is still divided 

 between the two systems proposed by them, although that of the latter, 

 having the advantage of less first cost, has been most generally adopted. 



Telford, the engineer of the Holyhead road, thought that the stone 

 should be laid upon a rigid foundation, and he therefore paved his road 

 bed with thin stones set on edge, and laid the covering on that, con- 



