A manual of the principles and practice of road-making: comprising the location, construction, and improvement of roads, (common, macadam, paved, plank, etc.) and rail-roads. By W. M. Gillespie ...

RErAINING WALLS. I87
no levellers shall be placed under a stone by raising it
from its bed. One-fourth of the wall shall be composed
of headers, which shall extend through the wall, where
it is not more than two feet thick, and from 2 to 4 feet
back for thicker walls. The whole shall be laid in hydraulic mortar, composed of the best quality of cement,
and clean sharp sand; and particular care shall be taken
to have each stone surrounded with moitar, and tho.
roughly bedded ir it."