349 



latter case they give a well-defined black cross. The spherulites are 

 sometimes arranged in bands. Spherulitic (nodular) felsites occur also in 

 the Mangerton group and in Benaunmore (Kerry). 



A typical " quartz-porphyry," that is a rock with conspicuous 

 porphyritic crystals, is described by VON LASAULX, from. Newcastle, 

 Co. Down. Under the microscope hornblende and biotite may be 

 recognized. The ground-mass is mainly composed of micro-pegmatite. 

 This rock would be a typical granophyre in ROSENBUSCH'S sense. 



A fine example of a biotite-quartz-felsite with indications of 

 granophyric structure in the ground-mass occurs at Allthomasreagh, 

 Co. Galway. 



Si0 2 



A1A 



Fe 2 3 



CaO 



MgO 



K a O 



Na,0 



Loss 



I. 



81-36 

 7-86 

 3-32 

 0-99 

 0-45 

 3-09 

 2-G3 



99-70 



II. 



78-40 



11-32 



0-92 



0-45 



0-48 



4-83 



3-09 



56 



100-05 



III. 



77-20 

 6-54 

 5-82 

 1-81 

 0-60 

 3-69 

 3-03 

 1-12 



99-81 



IV. 



71-52 

 12-24 

 3-16 

 0-84 

 0-39 

 5-65 

 3-36 

 1-20 



98-36 



I. Pale greyish green felsite. Bell Rock, Ovoca. 



II. Similar rock showing in places minute felspar crystals occasionally containing hollow 

 nodules filled with quartz and chlorite (HAUGHTON) . Carrickburn, Wexf ord. 



III. Felsite, Bonmahon, "Waterford. 



IV. Benaunmore, Kerry. Containing small quartz and felspar crystals. 



The above analyses were made by Dr. HAUGHTON.W They show 

 a close relation between the Welsh and Irish felsites. 



It is interesting to observe the occurrence in Ireland of nodular 

 felsites similar to those described by Professor BONNET and Mr. COLE. 



(1) Trans. Roy. Irish Acad. Vol. XXIII. (1859), p. 615. 



