24 Proceedings of the Royal Irish Academy. 



The examination of the epidiorite in this section was made by 

 Mr. Henry J. Seymour, b.a., of the Irish Geological Survey, and a 

 description thereof formed the subject of a communication by him to 

 the Dublin Microscopical Club (see Irish Naturalist^ 1896, p. 137). 

 In a subsequent letter to me he says : — 



" The description given by Teal on p. 198, £r. Petrography 

 (plates 18 and 20) applies perfectly to this rock from Killiney 

 Park (see especially plate 20, fig. 2). There is little doubt that 

 most of the feldspar, and practically all the hornblende, is secondary, 

 and that the rock has resulted from the dynamic metamorphism of a 

 basic pyroxene aphanite, or dolerite. The secondary character of the 

 amphibole is best seen in the slice parallel to the plane of schistosity, 

 and in which the ferro-magnesian constituent is seen to be actiuolite. 

 In this slide also the crushing out of the magnetic iron element is well 

 shown. Some zoisite occurs in the rock, and is probably derived 

 from the alteration of the original feldspathic constituent." 



The epidiorite outcrops on Yico Eoad, at a point about 80 to a 

 100 yards north of the gate which gives entrance to Yictoria Park, in 

 this locality. The water-channel along the footpath of the road 

 from the cross-roads at Ballybrack to Shanganagh is paved with 

 smooth, water-worn cobbles of this rock, which, in all probability, 

 were taken from the seashore, and which would tend to indicate the 

 presence of an outcrop of the rock on the shore, though probably now 

 completely covered over by the shingle and sand thrown up by 

 the sea. 



The mica schists which enclose the epidiorites, and with which 

 this is so intimately connected, presents characteristics which may 

 be found in certain beds of the Bray Head series of rocks, some 

 of them being of very fine grain, and therefore not at once recognis- 

 able as mica schist. In the railway cutting south of the Brandyhole 

 Tunnel, there is a well-marked outcrop of this mica schist ; it also 

 occurs in the beds which show themselves on the path about 90 yards 

 south of Lord Meath's gate-house. It would be very interesting to 

 compare this mica schist with that of Killiney Park, since the rocks 

 outcropping here might really be the same series as that found at 

 Bray Head, but in a much more metamorphosed state. A sample 

 of the Killiney mica schist was submitted to Mr. W. S. "Warren, 

 chemist, of Westland-row, for analysis, and he reported thereon as 

 follows : — 



" Received December 15th, 1896, from Prof. J. P. O'Reilly, c.e.. 

 Royal College of Science, Dublin, a sample of a crude rock, marked 



