Oathis work there are btiilt three thick Walls a croft it, that 
go frdm cme end of the Caufey to th^t her ^ founded upon the 
Body of the Mafonry, and running into the work of the Gallery, 
which they travcrfe crofs-wife. They are ancred and enchared, 
on the right and the left, in the rocks of the two skirts of the 
Valley. The/r/?Wall, which is at the beginning of theCaurey, 
M 1 2 feet thick at the end , being much broader below by reafon 
of the talu or flope : It is to be but 1 2 fathom high. The fec0p^d, 
to be more raifed, is 3 fathoms thick, and 2 5 fathoms high : It 
fends very near in the midft of the Caufey , 3 3 fathoms diftant 
from the firft. The third, which maketh the foot of the Caufey^ 
and is 31 fathoms ofi from the fecond, is 8 feet thick, and 
1 5 fathoms high. The empty fpace between the firft and fecond 
wall is to be filled with flones and earth well ramm'd together 
and made even/o that it may be cover'd with a bed of loam 6 feet 
thick, floping, and infenfibly defcending from the fecond to the 
firft Wall ; thatfo the water, thatlhall be madeto^ fwell to the 
height of 20 to 2 5 fathoms , fpreading it felf upon this ^/^^/V or 
flope, and to lean every whereon its center , maynotTpoil the 
Caufey. In the like manner is to be filled up the empty fpace 
between the fecond and third Wall ^ defcending alfo dope-wife 
from the fecond to the third, to ferve hr a buttrefs to the fecond^ 
that is to bear all the weight and force of the Water. 
All thefe Walls,and even thofe of the Gallery ,are to be counter- 
walled by a Wall of two feet thicknefs* Befides, the Gallery 
is to be counter- vaulted by another Vault ; and the intermediate 
empty fpaces are tohe done up with a clayie earth well ramm'd ; 
that fo, iri cafe that by any extraordinary accident the water 
fhould come to make any gap in the loam-bed, that is between 
the firft and fecond wail , the reft may by this means be pre- 
ferv'd entire. 
In the firft Wall there are Stones in toothings, from the top to 
the bbttom, on the right and left of tlie Aquedufis mouth, 
and of the Collieries window : And this is to make a Cavity 
, chamber-wife, four foot fquare. The Wall of this little 
ftruftute is to be fix feet thick , counter-walled with another? 
Wall two feet thi-ck, with a loam-bed between, to keep it 
fafr,^ Itlliall end on the top above the Gallery ^ flope-wife 
U a 11 u 2 zud 
