614 GREAT SERPENTINE-BELT OF NEW SOUTH WALES, V., 



1234. Radiolarian black chert. ^ The exact points at which these 

 1236. Radiolarian cherty shale. I rocks were collected are not stated. 



1235. Radiolarian shale. j They all came from the neighbour- 

 1233. Radiolarian limestone J hood of the Tamworth Common. 



Upper Devonian Baldwin Agglomerate. 

 Messrs. David and Pittman have pointed out that the matrix 

 of the agglomerate occurring on Cleary's Hill, near Tamworth, is 

 identical with the breccias of the Middle Devonian SeriesO). 

 The writer has shown that this is a part of the Baldwin Agglo- 

 merates, and that this similarity is a constant feature; indeed, 

 the agglomerates may be described as an " exaggeration of the 

 features of the breccias of the Tamworth Series," and when they 

 take on a rather finer grainsize than usual, it is impossible to 

 distinguish them from the Middle Devonian rocks. At certain 

 points they are full of rounded boulders, which decrease in size 

 as the strata are traced laterally. Each centre has about the 

 same assortment of boulders, though differences occur. The 

 boulders in the agglomerates at Cleary's Hill include the follow- 

 ing: — Porphyritic dolerite, with phenocrystsof albite and augite, 

 and a subvariolitic base; porphyritic spilite, with felspar-pheno- 

 crysts and minutely crystalline trachy tic base; felspathic dolerite; 

 porphyritic andesite, as described by Mr. Card(9, p. 36), in which 

 the augite has the peculiar brownish tint and appearance char- 

 acteristic of the brecciated augite-porphyrite described above 

 (p. 598); with decreasing amount of ferromagnesian minerals, 

 these dolerites pass into keratophyres, sometimes porphyritic, 

 but with a beautifully trachytic base (a very common rock), or 

 the base may be felsitic or cryptocrystalline; one example is 

 orthophyric and has no phenocrysts. There is also a quartz- 

 keratophyre, the phenocrysts of which are more or less corroded 

 quartz and albite, and the cryptocrystalline base contains long 

 patches of fibrous radiating felspar, and also fragments of mag- 

 netite-keratophyre. In addition, there are fragments of pre- 

 viously consolidated tuff, of limestone, and of chert. The matrix 

 consists chiefly of fragments of felspar, often zoned andesine, but 

 also albite, quartz, augite, ilmenite, and a still more minutely 

 comminuted paste of these minerals, with calcite, chlorite, etc. 

 The chemical composition of the matrix has been determined by 

 Mr. White. (See C, p.602). 



