538 MR. r. RUTLEY OX SOME OF THE 



tinous matter, probablj' derived from the decomposition of the 

 pyroxcnic constituents of the melaphyre fragments, and partly with 

 calcite. Judging from the texture of this tuff, it is probable that 

 the vent from which the lapilli were ejected was not very far 

 distant. 



No. YIII. S.AV. side of Caradoc, about 80 feet below the Camp. 

 (Amygdaloidal Melaphyre.) — A dark grey rock with small vesicles^ 

 some of which are filled with white and others with dark-green 

 matter. 



Under the microscope it is seen to consist of small lath-shaped 

 crystals of triclinic felspar, usually corroded and occasionally bent^ 

 together with magnetite (sometimes in octahedra, but mostly in 

 irregular grains), and a considerable amount of green matter, which 

 appears in some cases to be chlorite, but is not improbably a pala- 

 gonitic substance resulting from the alteration of interstitial glass. 

 The felspar-crystals lie irregularly in all directions. 



The vesicles are very irregular in form and some are filled with 

 chlorite or delessite (the optical sign in the direction of the fibres 

 is positive). Others are filled with calcite or quartz, while, at times, 

 a little chalcedony is present. The section is stained in places by 

 ferric oxide. 



No. X. S.W. side of Caradoc, about 100 feet below the Camp, 

 (Amygdaloidal Melaphyre.) — A compact dark brownish-grey rock 

 with very small vesicles, some containing quartz, others, a dark green 

 substance. Under the microscope it appears, when examined with 

 a low power, to consist of a felted mass of very minute felspar 

 crystals with opaque interstitial matter. The rock, in fact, shows- 

 the " pilotaxitic " structure of Hosenbusch, unless, indeed, the black 

 interstitial matter represents a once glassy groundmass now ren- 

 dered opaque by separation of magnetite, in which case the structure 

 would once have been " hyalopilitic." The vesicles contain chlorite 

 and quartz, and are very irregular in form. The section is traversed 

 by some delicate fissures now filled with quartz. 



Fig. 3 in PI. XIX. represents portion of a section of this rock. 



No. YII. S.E. side of Caradoc, low down, perhaps 150 or 200 feet 

 below the Camp. (Melaphyre.) — A rather pale greenish-grey to 

 brownish-grey, finely-crystalline rock, presenting no striking pecu- 

 liarities to the unassisted eye. Under the microscope it is seen to 

 be more coarsely crystalline than any of the preceding. 



The felspars, which constitute a large proportion of the rock, lie 

 in all directions and, from their extinction-angles, appear to be 

 labradorite, but in many cases they are partly converted into 

 kaolin. Much brownish or greenish matter is present, often filling 

 vesicles, in which case it usually forms divergent fibrous growths 

 and minute spherulitic aggregates which have a positive optical sign. 

 The section also shows rusty-brown patches of limonite, minute 

 specks of pyrites and apparently a little unaltered magnetite. The 

 felspars are often corroded and sometimes bent. 



No. XY. Little Caradoc, N.W. side, about 100 feet above the 



