530 KEPOBT— 1884. 



only to cleaved rocks of distinctly detrital, more or less argillaceous 

 materials. 



(A) England. 



(1.) Gornyiali : The Lizard Region. — -A considerable portion of the 

 peninsula south of the Helford river consists of nietamorphic stratified 

 rocks, which are well displayed in the fine cliffs forming its picturesque 

 coast ; inland, as a rule, exposures are few. The neighbourhood of the 

 Lizard Point is the only part where a complete and continuous section is 

 obtained, as masses of intrusive rock occnpy no small portion of the 

 district, and frequently rise directly from the sea. The metamorphic 

 stratified rocks may be divided into three groups, between which, how- 

 ever, there does not appear to be any very sharp line of demarcation 

 mineralogically, or any reason to suppose a discontinuity. Still, as each 

 is distinguished by marked and dominant mineral characteristics, it is 

 convenient to describe them separately. 



There is a good deal of rolling, much disturbance from the intrusion 

 of igneous rock, and faults are numerous in this district ; but probably 

 there are no very vast dislocations, and there are no indications of sharp 

 flexures on a large scale, or overthrows such as are frequent in districts 

 which are or have been mountainous, so that it seems safe to follow the 

 ordinary principles of lowland stratigraphy in working out the geology. 

 Enumerating the gi'oups in ascending orders, wc have — 



(a) Micaceous Group: characterised by rather compact dull green 

 schists, whose exact mineral composition cannot be readily decided 

 in the field, and by brownish mica-schists. These, as a rule, are com- 

 posed of very minute constituents, moderately fissile, sometimes with a 

 slightly ' flinty fracture,' not seldom very beautifully corrugated on a 

 small scale. The rocks, though the constituent minei'als are in many 

 cases very small (considerably less than "01" diameter), are completely 

 metamorphosed. The green schists, on microscopic examination, are seen 

 to be composed of an acicular light green variety of hornblende, of a green 

 filmy mica, or perhaps in some cases a chlorite, of quartz, of a little 

 magnetite, haematite, or pyrite, with epidote, a colourless garnet (rare), 

 and a kaolin-like mineral perhaps replacing felspar. The green minerals 

 and quartz are, however, the dominant constituents, so that the name 

 ' Talcomicaceous,' which was assigned to the series by De la Beche, 1 was 

 macroscopically appropriate, although, strictly speaking, there does not 

 appear to be any true talc. With it, but not largely developed, occurs a 

 brownish, slightly silvery mica-schist, in one place more coarsely 

 crystalline than the above, consisting chiefly of brown and green micas 

 (probably biotite and its alteration products), and paragonite (?), with 

 quarfz and a few small garnets. This group, as stated, is well exposed 

 in the southern cliffs of the Lizard from a short distance to the north of the 

 Quadrant Headland to the neighbourhood of the Lighthouse. Its strike 

 is roughly from WNW. to ESE., with a dip on the northerly side, but 

 there are many minor twists and rolls. The same group is exposed for 

 a very limited extent in the cliffs on the south side of Porthalla Cove. 2 



(b) Hornllenclic Group. — This group is much more extensively de- 

 veloped than the former in the cliffs forming the eastern and western 

 faces of the Lizard peninsula, and a considerably greater vertical thick- 



1 Report on the Geofogy of Cormvalland Devon, p. 29. 



- Associated with this is a band, a few feet thick, of a granitoid rock ; it may be 

 an intrusive vein-granite modified by compression, but looks as if it were interbedded. 



