178 STONE PAVEMENT CH. X 



pavement ; and for that reason flat gutter stones 

 should be positively interdicted, and the paving- 

 should be carried directly to the curb. 



' There is no occasion, in a well laid pavement, 

 for any crown to the street beyond what is neces- 

 sary to insure the centre not being lower than the 

 sides ; for that reason no crown of more than two 

 inches should be permitted in any street of sixty 

 feet in width, and less in a narrower street. 



' The excessive crown that most American city 

 streets have makes them uncomfortable to drive 

 upon, owing to the sliding of the hind wheels of 

 vehicles toward the ©utter. 



' In streets newly laid out and paved, the curb- 

 stones should have more slope than is usually 

 given them. In a five to seven-inch curb, the 

 slope of the face backward should be at least 

 two inches, so that wheels rubbing- against them 

 may strike the tire only, and not wear the wood 

 of the rims of the wheels. 



' The method of construction advocated is prac- 

 tically that of the streets of Liverpool, England, 

 which are now the best in the world. The con- 

 crete base possesses the advantage, among others, 

 that in laying gas or water pipes it can be cut 

 up in blocks, and relaid so as to insure a more 

 perfect patching than can be made on a soft 

 substratum. 



' Any pavement, however, is very much injured 

 ' by taking up a portion over a long trench, as the 



