SoLLAS — On the Structure and Origin of Quartzite Rochs. 187 



intrusions in the headland ; they are, however, truly clastic rocks, 

 and in addition to the quartz grains of which they are chiej&y 

 composed contain a good deal of rounded and angular fragments 

 of felspar, both orthoclase, microcline, and a triclinic felspar giving 

 low extinction angles (12°), with occasional flakes of muscovite and 

 a green chloritic mineral which resembles altered biotite. There 

 are other quartzose rocks besides these, which will be referred to 

 in my general account. 



LITERATUEE. 



(1) FiTTON, W. : 



"l^otice respecting the Geological Structure in the Yicinity of 

 Dublin ; mth an Account of some rare Minerals found in 

 Ireland."— Trans. Geol. Soc, Lond., vol. i., 1811, p. 269. 



(2) Weaver, T. : 



" Memoir on the Geological Relations of the East of Ireland," — 

 Trans. Geol. Soc, Lond., vol. v., 1819, pt. i., p. 269. 



(3) Weaver, T. : 



" Memorandum of Objects of Geological Interest in the Yicinity 

 of Dublin,"— Journ. Geol. Soc, Dublin, 1835, p. 9. 



(4) Kelly, John : 



"On the Quartz Rocks of the Northern part of the County of 

 Wicklow."— Jonrn. Geol. Soc, Dublin, vol. v., 1853, p. 237. 



(5) Close, Rev. Maxwell H. : 



" The Physical Geology of the l^eighbourhood of Dublin." — 

 Journ. Roy. Geol. Soc, Ireland, vol. v., 1880, p. 50. 



(6) KiNAHAN, G. H. : 



"Manual of the Geology of Ireland," 1878, 



(7) KiNAHAN, GeEAED A. : 



*' Some ITotes on the Geology of Bray Head. With a Geological 

 Map and Sections." — Proc Roy. Geol. Soc, Ireland, vol. vi., 

 1886, p. 188, PI. vii, 



(8) SoLLAS, W. J. : 



"Some Preliminary Observations on the Geology of Wicklow 

 and Wexford." — Rep. Brit. Assoc, Manchester, 1887, 

 p. 708. 



