134 LECTURE 



siclering that the stones would not in that case be forced out of place 

 into a yielding surface below. 



McAdaui, on the contrary, contended that the road covering thus 

 placed between the wheels and the unyielding pavement would be 

 rapidly ground to pieces, and that an elastic substratum is necessary to 

 prevent such an action ; he, consequent^, laid his road covering upon 

 the natural soil. Experience has not shown any great difference in 

 practice, although where first cost is no object, the Telford method is 

 perhaps somewhat preferable. 



On all stone roads careful attention must be paid to the repairs. The 

 usual way in this country of letting a road get into a bad condition, 

 and then undertaking general repairs, being much to be condemned. 

 The only proper way of keeping a road in good order is by a system of 

 constant repairs ; the moment that a rut or a depression is observed, 

 the stones in and around it should be loosened with a pick, and enough 

 fresh stone should be put into it to bring it slightly above the proper 

 level, the traffic soon smoothing it down. It is absurd to attempt to 

 mend a road by pouring stone into a deep hollow with smooth hard 

 sides, the stones having nothing to bind to ; and when they become 

 wet, they grind each other under the wheels into round pebbles, which 

 never can be made to hold together. 



No loose stones should be permitted to remain on the surface, where 

 they are exceedingly mischievous, but they should be either promptly 

 put back into the holes from which they came, or thrown on the stone 

 heaps out of the way. Such a supervision and maintenance of the road 

 will be found far more economical and satisfactory than any spasmodic 

 method of repairs can possibly be. 



A difficult engineering problem has always been to find a good 

 material for city streets. While macadamized roads are admirably 

 suited to the country, they are objectionable in town on account of the 

 dusty or muddy condition into which they invariably fall. Cobble stone 

 and broken stone pavements, as usually laid, are noisy and apt to get 

 out of repair. Those of cut stone, generally known in this country as 

 the Euss pavements, made of cubical blocks, are, perhaps, the worst 

 that have been yet tried; slippery, expensive, and most difficult to 

 repair. It is true that the tractile force required upon them is small, 

 owing to their smooth surface ; but this is nearly if not quite counter- 

 balanced by the extreme difficulty with which the draught animal moves 

 upon it. Any horseman who has ridden over such a pavement, must 

 have noticed that the animal moves as uncomfortably upon it as a 

 pedestrian upon smooth ice, and great fatigue is the consequence of 

 his endeavors to keep his footing, to say nothing of the absolute acci- 

 dents which constantly happen from falls. 



In the cities of Italy, (Florence, for example,) which are paved with 

 larger blocks of smooth hard stone, no rider thinks of mounting his 

 horse at his door, but has him led to the city gates to avoid the danger 

 of a fall ; and in such streets the carriage horses fall down and get up, 

 as a matter of course, probably not suffering as much as we might sup- 

 pose, since they know how to fall gently from long practice. 



Iron, cast into various forms, has been tried, but has not come into 

 general use, owing partly to its expense. 



