362 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1934 



Especially on important roads like the Appian Way the summa 

 crusta was made of hard, durable, wear-resisting stone like silex^ a 

 flintlike lava. This stone was laid in the form of pentagons, hexa- 

 gons, or irregular polygons, from 1 to 3 feet in diameter and some 

 6 inches in thickness. The upper surface was smooth, but the bedded 

 under side was left rough. The joints were fitted so closely as to be 

 scarcely discernible. This type of masonry was known as opus in- 

 certum. If volcanic silex was not available, other hard stone was 

 used, but dressed and laid in the same manner. Occasionally the 

 surface of the road was made of concrete. Sometimes blocks of 

 schistose stone, similar to Belgian block, were laid on edge. This 

 type of construction has been found upon a section of the Fosse Way 

 in Britain. The less important roads were frequently surfaced with 

 gravel. 



Cross Section of the Appian Way 

 by Cre sy 



Cross Section of the Appian Way 

 by Le^er 



FiGORB 5. — Cross-section of tbe Via Appia as shown by Cresy (6) and Leger (4). 



Side curls {uvibones). — The side curbs, or umhones, [15-a and 

 b], projected 18 inches above the 7?iargines, and were 2 feet wide. 

 They were built upon a foundation of large stones resting upon the 

 statumen. Mounting blocks {gradu^s) were placed along the side 

 curbs at regular intervals. 



Dimensions of the Via Appia. — The total thickness of the four 

 courses described above varied from 3 to 41/2 feet. The overall width 

 of the Via Appia at the surface was about 36 Roman feet (35 English 

 feet), of which the central agger constituted I51/2 English feet, the 

 two umhones each 2 English feet, and the two rnargines each 7% 

 English feet. Cross-sections of the road, by Edward Cresy (^), in 

 1847, and by Alfred Leger (4), in 1875, are shown in figure 5. 



