366 
EMBANKMENTS. 
Steeper slope than three feet horizontal for one foot 
perpendicular. In cuttings in chalk or chalk-marl, 
the slopes will stand at one to one. In sandstone, 
if it be solid, hard, and uniform, the slopes will 
stand at a quarter to one, or nearly perpendicular. 
If a sandstone stratum alternates with one of clay 
or marl, it is difficult to say at what rate of inclina- 
tion the slopes will stand ; this will, in fact, depend 
upon the inclination of the strata. If the line of 
the road is p' .rallel to the line of the bearing of the 
strata, in such cases large masses of the stone be- 
come detached and slip down over the smooth and 
glossy surface of the subjacent bed. There are 
many instances of slips in sandstone and marl stra- 
ta, under such circumstances as those now descri- 
bed, where the slopes are as much as four to one. 
If the road is across such strata, or at right angles 
to the line of bearing, the slopes may be made 
one and a half to one ; but if the strata are hori- 
zontal, even should there be thin layers of marl 
between the beds of stone, the slopes will stand at 
a quarter to one. But it will be necessary, if the 
beds of marl exceed twelve inches in thickness, to 
face them with stone. In the Oxford clay, which 
covers so great a portion of the middle counties 
of England, the slopes should not be less, in any 
instance, than two to one, and even in some parts 
of this formation they should be made three to one 
if the cuttings are deep. In all such cases, if any 
beds of gravel or sand are found intermixed with 
the clay, drains should be cut along the top, and 
even in the sides of the cuttings ; for if this precau- 
tion be not taken, the water, which will find its 
way into the gravel, will, by its hydrostatic pres- 
sure, force the body of clay down before it, and 
slips will take place even when the inclinations 
are as much as four to one ; and, when this occurs, 
it is extremely difficult to re-establish them. In 
limestone strata, if solid, slopes will stand at a 
