Yol. 55.] PETROGRAPHY OF THE ROCKS OP COJJTGLETON EDGE. 557 



and perhaps of augite, in a yellow or red matrix. The vesicles are 

 large and sometimes contain small lapilli. The block is probably a 

 fragment of lava. 



Another block (984) is of a dark and fine-grained limestone 

 surrounded by, and passing into, green lapilli cemented by calcite. 

 The dark limestone contains a few vesicular and non-crystalline 

 lapilli altered to calcite, and two fragments of felspar. The tuff 

 adherent to the limestone consists of lapilli and organisms mingled 

 together. The lapilli are sometimes vesicular and free from crystals, 

 and are often more or less rounded. In other cases they contain 

 felspar-micro] iths and have a yellow isotropic base. Numerous 

 strings of calcite traverse the microscopic slice. 



A block of coralline limestone from the agglomerate (985) 

 is composed partly of a large coral, which occupies a considerable 

 area of the thin slice, and partly of a limestone containing fora- 

 minifera, MonticuUpora, and other organisms, with a few lapilli. The 

 latter are sometimes vesicular and non-crystalline, and in other cases 

 contain felspar-microliths and probably small olivine-pseudomorpbs. 

 They are often isotropic, and many of them are subangular in 

 shape. 



2. The Tuffs in the Brook north of the Quarry. 



The following seventeen specimens were obtained by Dr. Hind 

 from about 500 yards north of the limestone-quarry (see p. 551) 

 and in the quarry itself. 



Specimen C, tufaceous limestone (1011), from a bed 2 feet 

 thick, is a rock containing fragments of organisms and pieces of 

 previously consolidated limestone and lapilli. The lapilli, which 

 for the most part have undergone alteration, are in some cases 

 highly vesicular,- and in others contain a few felspar-microliths and 

 probably pseudomorphs of olivine. 



Specimen B, tufaceous limestone (1010), from a bed 2 feefc 

 thick, is hard in a hand-specimen. It consists of a fine-grained 

 partly crystalline limestone, with a few organisms and some 

 lapilli. Some of the latter are vesicular and non-crystalline, others 

 contain felspar-microliths. The fragments of igneous rock are 

 often altered to calcite. 



Specimen A, calcareous tuff (1009), from a bed 1 foot 11 

 inches thick. It contains organisms and tuff-fragments. The 

 latter are plentiful, and form the greater portion of the thin slice. 

 Many of them are vesicular and altered to calcite. Some of them 

 contain feJspar-microliths and pseudomorphs of olivine. They are 

 not in a fresh state of preservation, and are often subangular. 



Specimen D, tufaceous limestone (1012), a few feet below A. 

 It is a limestone containing corals, foraminif era, and other organisms, 

 with a few small lapilli, which are often altered to calcite, and nob 

 always readily distinguished from the limestone surrounding them. 

 Pew of them contain felspar-microliths. 



