BV W. X. BKXSON. 367 



These two rocks clearly belong to the same group of dolerites as 

 figured in Part iv., Plate xxv., fig. 2. 



The next mass of dolerite (No. 1393), half a mile to the south- 

 east of the point of occurrence of No. 1394, is a rock of medium 

 grain-size, with all)ite-felspar, intei*stitial quartz occasionally 

 granophyric, and augite almost completely changed to chlorite; a 

 little magnetite also is present. 



The dolerite in the belt of rocks which crosses Cope's Creek, is 

 exemplified by No. 1376. Though the felspar in this rock is now 

 a very dusty albite, it has certainly been derived from a more })as:c 

 mineral. It is sometimes a little spongy, containing prehnite, wliieli 

 also occurs interstitially in large clear patches. The augite is 

 entirely replaced by cldorite; ilmenite and apatite occur in ratlier 

 large grains. 



The Por])]i(/n'tic Dolerites, generally closely associated with the 

 Nemingha limestone, may be illustrated by the description of three 

 specimens. It occurs in Portion 59, immediately east of tlie lime- 

 stones, and is a fresh-looking, dark green rock with phenocrysts of 

 felspar and augite(No.l407). The felspai* is an acid hibradorite 

 and is only slightly zoned. The augite-phenocrysts are, in parts, 

 quite fresh, while some are completely changed to pseudomorphs of 

 chlorite, and carbonates in one instance, with a further replacement 

 of the centre of the pseudomorph by quartz and chalcedony. 

 There are also small phenocrysts of magnetite. The base has a 

 spongy fabric similar to that of quartz-keratophyre. It consists of 

 short laths of dusty labradorite, an abundance of minute crystals 

 of magnetite, and a good deal of inter.^titial quartz. 



