J. J. H. Teall — Origin of Banded Gneisses. 



491 



represented in Fig. 5. It consisted of parallel bands and narrow 

 lenticles of foliated gabbro, granite and diorite. Fig. 6 represents 

 the relations of granite, diorite, and gabbro in a mass which ex- 

 hibited no parallel structure. In Figs. 5 and 6 the space left clear 

 represents granite, or at any rate a rock of granitic composition ; the 

 dotted portions represent diorite, and the portions indicated by fine 



Fig. 4. Granite in Gabbro, Pen Voose. Block 6 feet long. 



lines gabbro or gabbro-schist. Fig. 5 represents a mass four feet 

 and Fig. 6 one three feet in height. 



I submit, therefore, that the rocks of the Lizard District referred 

 to in this communication, and which constitute the greater portion 

 of Prof. Bonney's granulitio series, are of igneous origin and that 

 the parallel structure which characterizes many of them has nothing 



Fig. 



Fig. 6. 



to do with stratification in the ordinary sense of the word, but is 

 a consequence of the deformation to which the original rock -masses 

 have been subjected. It is undoubtedly true, as Prof. Bonney 

 has pointed out, that many of the rocks are largely composed of 

 broken crystals, and may be said therefore to possess a clastic 

 structure if we use the term clastic in its etymological sense. But 

 this is no proof that the fragments have been deposited as such. 

 The original minerals may have been broken during the deformation 

 of the rock-masses. This I believe is what has actually taken place. 



