460 OH P1TCHSTOHES AND TEKLITES FROM SHROFSHIKE. 



their numerous varieties the precise analogues of the ancient 

 volcanic rocks of Shropshire. 



EXPLANATION OF PLATE XX. 



Fig. 1. Portion of a thiu slice of perlitie pitchstone from Meissen. The 



narrow shaded bands represent an incipient alteration along the 

 lines of fissure. 



2. Another portion of the same slice. 



3. Part of a thin slice of perlite from Schemnitz. 



4. Perlitie spheroid from Cabo de Gata. see p. 4o2. 



Ek Section ot perlite from Schemnitz. showing parallel and cross joints, 

 with general grouping of the perlitie spheroids, see p. 4^l2. 



6. Ancient perlitie pitchstone. ""Lea Koek." near Wellington, showing a 



similar original structure. The shaded pans represent a green- 

 coloured product of alteration, see p. 456. 



7. Section of spherulitie perlite from Kremnitz. described p. 453. 



5. Section of spherulitie pitchstone from Lea Eoek. containing bands 



of spherulites and streams of mioroliths in a transparent perlitie 

 matrix. 

 9. Diagram of spherulite. described p. 4o4. 

 10. Spherulite in ancient pitchstone. Lea Eoek. containing two crystals 

 of felspar, and traversed by a vein tilled with a substance having 

 similar optical characters to the devitrined matrix, see p. 4o7. 



The figures faithfully represent the originals as seen with the magnifying 

 powers indicated, with the exception of the fibrous crystallization of the sphe- 

 rulites. which is. of course, greatly exaggerated. 



Discussion. 



Mr. "Wakingtox W. Smyth thought that, with regard ro the rocks 

 of the Lizard Point. Air. Bonney's paper would carry conviction to 

 the minds of many who had been led to different views by the 

 works of previous writers. The facts brought forward seemed to 

 correlate these rocks with others which have been examined in 

 Sweden and Norway, in the south of Spain, and in Elba. 



Prof. Junn. referring to Mr. Allport's paper, said that the simi- 

 larity of these ancient rocks to those of Tertiary times extended to 

 the most minute details. The unity of character so long ago recog- 

 nized among stratiried rocks of different ages was now being ex- 

 tended to the igneous rocks: and these also would in time be corre- 

 lated according to their respective ages. 



The Purs i text inquired whether Mr. Bonney had met with indi- 

 cations of gas-passages in the serpentinous rocks, such as might 

 simulate Eozoon. 



Ke\\ T. G. Boxxrr stated that he had examined the serpentines 

 of Elba. With respect to Mr. McPherson's paper referred to. lie 

 said that some of that gentleman's figures might be taken as repre- 

 senting the Lizard serpentines. In reply to the President he stared 

 that he had seen gas-passages, but nothing resembling E : 

 although in the first stages of the decomposition of olivine the num- 

 muline layer sometimes seemed to be simulated. For his own pair 

 he believed in the organic nature of Eozoon. 



