Uses of the Round Towers of Ireland, fyc. 



181 



ways, namely, the inclined sides, and the horizontal and semicircular heads ; 

 the horizontal head, however, so common in the doorways, is but of compara- 

 tively rare occurrence in the windows ; while, on the other hand, the pointed 

 head formed by the meeting of two right lines, which is so rare, if not unknown, 

 in the most ancient doorways, is of very frequent occurrence. I may observe 

 also, that the horizontal-headed window and 

 the triangular-headed one, are usually found 

 in the south wall of the chancel, and very 

 rarely in the east wall, which usually con- 

 tains a semicircular-headed window, the 

 arch of which is often cut out of a single 

 stone, as in the annexed example in the 

 church of the Trinity, at Glendalough. In 

 many instances the head is also formed of 

 two stones, as in the following example in 

 the east window of the oratory at Gallerus, built without cement : 



In some of the most ancient churches examples may also be found of windows, 

 in which the arch is formed externally, as in the doorways, of several stones, par- 



