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IV. 



OBSERVATIONS 071 /A^THEORY 



o/' WALLS^ wherem some parti- 

 culars are investigated ^luhich have 

 not been coiisidered by writers 

 on fortification. By William 

 LambtoNj hieutenant in His Ma- 

 jestys 33d Regiment of Foot. 



R. MuLLER, and others, in treating on the 



M 



theory of walls, have confi- Ftg. I. 



dered the part of the wall D C 



ABCD which is above the 

 ditch, as one piece of folid 

 mafonry, without having any 

 reference to the part FGBH, 

 which is funk in the ground, j^ 

 and they have inveltigated 

 the force neceffary to fuftain F 

 the earth BCT, in equilibrio, 

 and have given dimenfions for the wall ABCD, fo as 

 to equal the faid force ; but they have negledled 

 taking into conlideration the tenacity of the mafonry 

 in the line AB, where the wall is fuppofed to break 

 off, and turn freely on the point A. On examining 

 this fubjedl it appears evident that, if the cement be 

 good, a confiderable additional force, to that which 

 would equal the weight of the wall, refting againft the 

 point S, muft be reciuired to break the mafs in the line 



AB, 



