116 



REPORTS ON THE STATE OF SCIENCE. 



Composition and Origin of the Crystalline Rocks of Anglesey. — Sixth 

 Report of the Commit'ee, consisting of Mr. A. Harker {Chairman), 

 Mr. E. Greenly (Secretary), Dr. J. Horne, Dr. C. A. Matley, 

 and Professor K. J. P. Orton. 



During the autumn, not long after the presentation of the last report, 

 the map of Anglesey, in connection with which the work of this Com- 

 mittee has been done, was completed. The presentation of this report 

 finds some of the analyses already incorporated into the manuscript of 

 chapters of the forthcoming memoir, which will accompany the map. 



As indicated in the report for 1910, the principal part of Mr. 

 Hughes' rather limited opportunities for research work has been given 

 to rocks belonging to the great Schistose Complex, chiefly with a view 

 to determining the origin of the completely reconstructed metamorphic 

 types. 



No. 638 A. Ysgubor Fawr, Capel Soar. 



Si0 2 



A1 2 3 



Fe 2 3 



FeO 



CaO 



MgO 



K 2 



Na,0 



H,0 (at 110°) 



H 2 (above 110°) 



998-8 99-90 



This is a chloritic siliceous schist of sedimentary origin, with sur- 

 viving sedimentary structures, that is the ' country rock ' of the S.E. 

 part of the central district of the Island. In it occur many quartzites 

 and limestones, as well as the basic schist whose analysis was given in 

 the last report. On its further side it adjoins mica-schists that are 

 completely reconstructed. 



No. 126 A. Homblende-epidote Schist, Sam Fraint. 



I. 



SiO, 45-86 



18-85 



5-73 



. 5-43 



11-61 



6-73 



2-00 



2-63 



HjO (at 110°) 0-05 



H 2 (above 110°) 1-34 



A1 2 3 



Fe 3 3 



FeO 



CaO 



MgO 



K 2 



NajO 



II. 



45-89 

 18-76 

 5-70 

 5 45 

 11-68 

 6-80 

 1-99 

 2-59 

 006 

 1-37 



100-23 100-29 



This is a hornblende-epidote schist of the S.E. district, in which 

 occur also the beautiful glaucophane-schists (analysed by Dr. Washing- 

 ton), and also mica-schists of disputed origin. The analysis completes 

 a series from that district, among which are those from the pillowy 

 diabase lavas. 



