Book II. 



PAVED ROADS. 



601 



3713. Various improvements in laying pavements have recently been devised, such as 

 laying the stones dry on clay ; using square stones, or stones equally wide at bottom as 



at top ; using stones alternately wider at bottom and top, 

 and joining them with cement (Jig. 556.); paving on plates 

 of iron, wood, or stone, or on a mass of masonry, &c. If 

 pavements in towns did not require to be frequently lifted 

 on account of sewers, and water and gas pipes, paving in 

 this manner on a solid foundation would certainly be the 

 best mode; but as things are, and even probably if pavements did not require to 

 be frequently lifted, M' A dam's roads are found greatly preferable for all broad streets, 

 and where care is taken to keep them clean and in complete repair. In Britain, at 

 least, they will probably soon supersede all common pavements, and all other descriptions 

 of common roads. 



3714. Large blocks of granite (Jig. 557.) have been substituted for common-sized paving 

 557 / ^ stones ; each block is two or more feet square, nine inches deep, 



and channelled on the surface in imitation of common-sized 

 paving stones. These are found to answer much better than 

 the cast-iron plates ; but they are liable to the same objection 

 as to leverage ; are difficult to replace properly ; and as the 

 raised pannels between the grooves will in time wear down 

 to the level of the grooves, they cannot be considered so 

 durable as common square stones, which, after all, appear 



the best for general purposes, and, at all events, for paving the middle or sides of 



highways. 



3715. Blocks of stone, and also of timber, have been proposed to be laid in iron boxes ; 

 but the effect of the granite blocks laid down in Fleet-street does not warrant the ex- 

 pectation of any advantage from either of these modes. Where nothing but light car- 

 riages pass over a road, no material is more agreeable than blocks of wood set endways, 

 as is done in many parts of Russia and Germany ; and this mode of paving may, there- 

 fore, be considered very suitable for private court-yards, or stable-yards in country resi- 

 dences. (Newton's Journal, vol. vii. p. 197.) 



3716. The defects of common pavement, and the theory of its wear, are thus given by 

 Edgeworth. " Stones, in a common pavement, are usually somewhat oval, from five to 



seven inches long, and from four to six inches broad. They 

 are laid in parallel rows on the road (fg. 558. c, d), or alter- 

 nately (a, b), as bricks are laid in a wall. On the first sort 

 of pavement, wheels slip from the round tops of the stones 

 into the joints between, and soon wear away the edges of 

 the stones, and their own iron tire. By degrees, channels 

 are thus formed between some of the stones, and in time the 

 pavement is ruined. 



3717. On the second sort of pavement (a), b, where the 

 stones are placed alternately, to prevent the injury to which 

 the former method is liable, the wheel (f) sliding sideways, 

 makes a channel between two stones, and is then obliged 

 to mount from the groove which it has made, to the top of 

 the stone opposite to it ; when it has attained this situation, 

 the wheel may slide sideways, or may go forwards over the 

 top of the stone, till it drops into the interstice between the two next stones. By con- 

 tinual wearing, these ruts become so wide and deep, that the wheel does not touch the 

 stones on either side, nor does it reach the ground between them, bi't it bounds from 

 one stone to the other, thus jolting the carriage in every direction. This method is not 

 at present in use. 



3718. In the pavements last described, the stones are but of a small size; but if flat 

 stones of twelve or fourteen inches long (e) are well laid, wheels are not liable to slide 

 into the joints ; and if such stones are laid with their longest sides crossing the road, 

 they are less liable to injury ; but still narrow wheels sometimes fall into the joints 

 between the largest stones, and having in time worn away their own edges, and those of 

 the stones, they will act like wedges, and will displace the stones. No pavement, of the 

 best stone that could be procured, can long resist this action of a narrow wheel. And 

 the only effectual means of preserving pavements is, to increase the breadth of all wheels 

 to at least three inches. Were no wheels narrower, a cheap and durable pavement might 

 be made of flat stones, not more than three inches square, provided they were eight or 

 nine inches deep, to give them reciprocally lateral support ; for the tire of such broad 

 wheels could never sink between the joints of the stones." (Edgeworth.) 



3719. Various improved methods of paving have been lately brought into notice. 

 About 1811 or 1812, we suggested the idea of placing the stones on a foundation 



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