Vol. 56.] THE IGNEOUS ROCKS OF COUNTY WATERFORD. 657 



35. The Igneous Rocks of the Coast of County Waterford. By F. 

 R, Cowper Reed, Esq., M.A., F.G.S. (Read May 23rd, 1900.) 



Contents. 



Page 



I. Introductory 657 



II. Geographical Distribution and Geological Development 



oftheEocks 658 



a. The Felsitic Hocks. 



b. Necks of Non-Volcanic Materials. 



c. The Basic Sills and Vents. 



d. Intrusions of Dolerite. 



e. The Smaller Intrusive Veins. 

 /. Intrusions of Various Types. 



III. Petrological Notes 678 



a. The Felsites. 



b. The Diabases and Dolerites. 



c. The Rocks of the Smaller Intrusive Veins. 



d. The Felsite-Porphyries. 



e. The Augite-Porphyrites. 

 /'. Miscellaneous Types. 



IV. The Age of the Rocks 690 



V. Conclusion 692 



I. Introductory. 



In a former paper on the Waterford coast l the Ordovician sedi- 

 mentary beds and the contemporaneous lavas and tuffs were 

 described. It is now proposed to give an account of the other 

 igneous rocks which occur along the coast, on which I have been at 

 work for the last seven years during repeated visits. 



The great complexity of their relations has been noticed by many 

 observers, and while the following account does not claim to be 

 exhaustive, an attempt is here made to determine the order and 

 relations of the principal outbursts of volcanic energy and to describe 

 some of the characters of the rocks. 



The bibliography of the Lower Palaeozoic rocks of County "Water- 

 ford has been given in detail in my previous paper. With regard to 

 the igneous rocks, however, the papers by Weaver, 2 Jukes, 3 and 

 Haughton 4 may be referred to, and the accounts by Mr. McHenry & 

 Prof. Watts, 5 and Sir Archibald Geikie 6 may be specially mentioned. 

 The Geological Survey Memoir for Sheets 167, 168, 178 & 179 is a 

 fund of information ; and further reference to the igneous rocks 

 will be found in papers by Haughton, 7 A. von Lasaulx, 8 and Dr, Hatch, 9 ' 

 and in Mr. Teall's ' British Petrography ' (pp. 248, 348). 



i Quart. Journ. Geol. Soc. vol.lv (1899) pp. 718-71. 



2 Trans. Geol. Soc. ser. 2, vol. v, pt. i(1837) p. 1. 



3 Journ. G-eol. Soc. Dubl. vol. v (1852) p. 147. 



4 Trans. Eoy. Irish Acad. vol. xxiii (1859) p. 563. 



5 Guide to the Collections of Rocks & Fossils belonging to the Geological 

 Survey of Ireland (1895). 



6 « Ancient Volcanoes of Great Britain ' vol. i (1897) pp. 245-51. 



7 Journ. Geol. Soc. Dubl. vol. vii (1857) p. 282. 



9 ' Petrogr. Skizzen aus Irland ' Tscherm. Min. u. Petrogr. Mitth. ser. 2, 

 vol. i (1878; p. 446. 9 Geol. Mag. 1889, p. 545. 



Q. J. G. S. No. 224. 2 t 



