Thickness.) Cement and Materials of Walls. 199 



ground story, were arched over with brick. The arches 

 were either 9 or 14 inches thick ; and a sHght pine floor, 

 was laid over the cro\vns of these arches. Through 

 this, access was easy to the cavities; between the 

 crowns and springs of the arches. The bricks could 

 be worked loose, out of these flimzy arches, with a knife, 

 or any pointed instrument; and access to the cellars 

 afforded.* 



The trap doors, or apertures in the floors of their 

 apartments, made by the prisoners, were covered from, 

 view by blankets : and most commonly, by those off 

 fatigue, lying over them. With common cord wood 

 sticks, hardened by paitial burning, the detachments 

 of sappers and miners^ under the floors, and in the cel- 

 lars, worked loose the inner crust, or face, of the wall ; 

 pulled out with their hands, without the aid of tools, 

 the interior materials, and displaced the external ma- 

 sonry. Thus passages for escapes were afforded, 

 through a long period, before discovery : and the affair 

 was conducted with generalship. So that only a few 

 eloped at a time, lest a detection should blow up the 

 scheme too suddenly. The last fugitive always closed 



* The mortar of these arches was so overcharged with lime, 

 Ihat it could be crumbled to pieces by the fingers of several 

 people who examined it. It is to be hoped, that time has 

 cured this defect. The absorbent quality of brick, permits 

 richer, and requires more fluent mortar; but this is often 

 overdone. Contract builders think they stint the mortar, to 

 save lime, when they involuntarily hit the right point. But 

 they do not fill the joints ; and injuriously save in quantity. 

 They should be obliged by the contract, to grout tlie work. 



