96 PALEOZOIC EOCKS OF THE KILBEIDE PENOSULA. [Feb. I9I2. 



We quote below an aiialj'sis of one of the Kilbride spilites, and 

 for comparison add two analyses of British spilites as quoted by 



Mr. Dewey & Dr. Flett in their paper on British pillow-lavas 

 in the ' Geological Magazine '.^ 



I. II. III. 



SiO., 4980 47-56 51-31 



TiO; 1-70 2-40 1-92 



AlA 17-94 14-27 1267 



• Fe;03 2-37 1-63 0-54 



FeO 6-74 6-80 7-99 



MnO 0-30 0-45 



CaO 900 10-95 8-17 



MgO 4-02 4-90 2-19 



Na,0 4-03 4-61 5-21 



X.,0 0-20 0-27 0-54 



P.,03 0-19 0-90 



CO, 1-28 2-95 6-15 



Wa'rer at 105° C 0-10 0-42 0-04 



Water (combined) 3-54 2-65 2-31 



Totals 100-72 99-90 100 39 



I. Spilite fi-om Kilbride, analysed by J. Weintraube. 

 II. Pillow-lava. Tregedden (South "^Cornwall) : omittiug (CoXi)O 0-08, 

 FeS., 0-22, Fe-S^ 005. Anal. E. G. Radley. 

 III. Pillow-lava, Argyllshire: omitting FeS., O'SO, Fe.Sg 0-17. Anal. E. G-. 

 Radley. 



A comparison of these analyses shows how similar the Irish 

 spilite is in composition to the Cornish rock. 



It is interesting to recall that we found small intrusions of a 

 spilitic rock in the Arenig Series in the Tourmakeady area, 

 which Dr. Flett, after microscopical investigation, stated to liave 

 the essential features of the Mid-Devonian lavas of the Plymouth 

 area.^ 



(/) The TuflPs. 



Pew sections were cut of these rocks, their interest lying chiefly 

 in features which may be observed in the field. As compared with 

 those of Tourmakeady and Glensaul, the most interesting characters 

 are negative ones, namely the absence of limestone-breccias and the 

 slight development of gritty tuffs. The coarse breccias so extensively 

 developed at Kilbride differ from those of Glensaul, in the fact that 

 the blocks consist of spilite nearly as frequently as of felsite. In 

 many of the fine tuffs, also, the little ashy particles are frequently 

 of spilite. Only at one point (109), a small exposure a third of a 

 mile north-north-east of Lough Mweelaun, occur silicified tuft's 

 similar to those found in the Mount Partry Beds of Glensaul. 



Geol. Mag. dec. 5, vol. viii (1911) p. 206. 

 Q. J. a. S. vol. Ixv (1909) p. 136. 



