114 Proceedings of the Royal Irish Academy. 



Latin cross cut in relief on the soffit of the lintel of the western door- 

 way may have been intended to fix the point where the observer 

 should stand in order to make the observation of the rising sun on the 

 horizon, on the day of equinox, as indicated in the sketch of the 

 doorway and eastern opening in question (Plate II). It may also 

 be observed that the aperture of this eastern window would allow of 

 the sun being seen through it from the point referred to, at its rising, 

 on one day only in the year. This use of the cross would so far 

 correspond with that of the incised cross on the rock in front of the 

 church on Dalkey Island, referred to in my Paper on that building. 

 Reference may also in this respect be made to the woodcut of the door- 

 way in St. Mary's church, Glendalough, given in Joyce's Social 

 History of Ancient Ireland," vol i., p. 318 (and mentioned as being 

 taken from the Journal of the R. Soc. Antiq. Ireland, 1900, p. 310); in 

 this case the diagonals of the soffit are represented in relief, and their 

 intersection at the centre is marked by a rosette in relief. The other 

 details are almost identical with those given in the sketch of Killiney 

 church herewith submitted, and suggest an intention of obtaining a 

 correct line of orientation or observation for equinox. That there was 

 such an intention of making use of this eastern opening of Killiney 

 church for the observation of the rising sun on the day of equinox is to 

 some extent supported by the relation of the eastern window of the aisle 

 to the western doorway thereof. This window is not only wider and in 

 every respect more recent-looking than that of the chancel, but it was 

 also divided and protected by a middle vertical bar, of which the socket 

 is still visible in the sill of this window. !N'ow, a line through the 

 middle of the western doorway of the aisle, and through the bar of the 

 eastern window thereof, gives a true east-and-west line ; and it is 

 probable that it was used for a more correct determination of the 

 equinox than could be attained by the use of the corresponding line of 

 the nave and chancel already considered. 



The church of St. Nessan on Ireland's Eye was also examined; but 

 having been fully and critically described by Mr. Cochrane in his 

 Paper which appeared in the Journal of the Roy. Soc. of Antiquaries 

 {Journ. R. Soc. Antiq. Ireland, 1893, p. 396), there was only left for 

 examination the evidences existing as to the unit of measurement 

 employed in the construction of the building. As pointed out by 

 Mr. Cochrane, the restorations have been such, and so extensive, that 

 one can hardly even trust the present thicknesses of the walls as repre- 

 senting those of the original walls. The western doorway gave a 

 thickness of wall at the sill of 82-5 cm. (2' 8-88") ; while, under the 



