O'Reilly — Old Churches of Dalkoy Town and Idand. 219 



At the side door of the south transept entrance is placed the 

 following inscription on a shab let into the wall : — 



Ohiiquitas EcddijJtin : Maxima. 

 23°: 2^8': 40" 



Fait par Claude Langlois 



Ingr. aux Gale'-.ries du Louvre 



MDcdxLIV 



This remarkable piece of work demonstrates, by its arrangement 

 and inscriptions, the traditional acknowledgment of the Papal and 

 Patriarchal admonitions as to the observation and determination of the 

 equinoxes and solstices, in view of the correct definition of the paschal 

 time, and of the festival connected therewith. That similar arrange- 

 ments may still exist in other churches and cathedrals on the 

 Continent, particularly in those of Rome, there is reason to believe; and 

 considering the influence that the Continental ecclesiastical customs 

 had on the early churches of Ireland, it is presumable that in many 

 of these some such arrangement was provided for. 



The examination of the south-eastern opening of Dalkey Town 

 old church seems to me to point to such a use of the beams of sunlight 

 which may pass through the upper and lower compartments of this 

 window, of which an elevation, section, and interior elevation are 

 submitted herewith (PL XYI., figs. 2, 3, 4, and 5). It will be observed 

 that the opening is divided towards the middle of its height by a 

 cross-piece or sill ; exteriorly, this and the lower sill are of roughly- 

 fashioned slabs of granite ; but the middle sill, while showing a 

 granite slab exteriorly, presents on the inside a mica-schist slab, which 

 naturally oSers relatively smooth surfaces and sharp straight edges. 



Now the thickness of the wall, taken in conjunction with the 

 height of the opening in the clear, determines the conditions under 

 which sunbeams are able to pass through these openings, and the 

 forms determined by the beams of light on the floor or opposite wall. 



