A TOUR ROUND NORTH WALES. 171 



4 



a zigzag fafhion, and then poured boiling 

 mortar upon them, which, from it's flu- 

 idity, infmuated itfelf into the many open- 

 ings and hollows of the work, and thereby> 

 from it's ftrength, bound the irregular 

 pieces of ftone frequently ufed, into a firm 

 and folid wall. In making the mortar 

 they mingled fand with the lime, unre- 

 fined by the fkreen, and charged with all 

 it's gravel and pebbles, and even fome of 

 the mortar, on breaking it, has been found 

 tempered with pounded brick. The mor>- 

 tar ufed in thefe walls has acquired from 

 time almoft the hardnefs of ftone. 



Along the walls are three parallel rows 

 of circular holes, each nearly three inches 

 in diameter, which pafs through the whole 

 thicknefs j and at the end are others fimi- 

 lar. There has been much learned con- 

 jecture as to the defign of thefe holes, 

 fome have fuppofed them to have been 

 ufed for difeharging arrows through at the 



enemy, 



