. C 2217 ) 
being founded upon a foot fquare Quarry of Brick • and 
upon the head of every Pillar was fixed a large Quarry of 
2 foot fquare, hard almoft as Flint, as mod of thofe Fo> 
man Bricks are, and within as Red as Scarlet, and fine as 
Chalk. Thefe pillars were to fupport a double Floor 
mac of very ftrong Mortar, mixed with courfe Gravel 
and bruifed or broken Bricks : The firft of thefe Floors 
was laid upon the large Quarries, and, when dry, the 
fecond Floor was laid upon it. 
But firft there was a Range or Rank of Tunnel-Bricks, 
fixt with Iron cramps up to the Wall within, with their 
lower ends level with the under fides of the broad Quar- 
ries, and their upper ends with the furface of the upper 
Floor 'j aim every Tunnel had alike 3 oppofite Mortice- 
holes, onr on either fide, cut through for a crofs paffage 
to difperfe the Heat amongft them all. The Form of the 
whole will be better underftood by infpeding the Figures. 
Explanation of the Figures, 
Fig. r. A. B. C- D. is the Ground Plat, oa which the. 
Pillars of Brick ftand. 
Fig. 7 . E. F. is one of the faid Bricks which are in' 
Numb. 24. 
Fig. 3, G. H. I. R. is. the Ceiling of Square. Tiles, which* 
lye upon the Heads of the fquare Pillars. 
Fig. 4. L. M. N. Q. P. Q. i-s the Sweating-Houfe, in 
Perfpedive, fliewing in part the Manner Of the Floors 
and Pillars as they were placed. 
Fig. 5. R, S. T. tl, is the double Floor, whole upper 
farfacelies even with the tops of the Flews in. the Per- 
fpedive Draught. 
Fig. 6 . W. X. Is one of the Flews, or Tunnel-Bricks,, 
. M. M 
