564 DK. J. W. EVANS ON MECHANICALLY-FOEMED [Aug. I9OO, 



in thin sections of the rock, and in the residue obtained on treat- 

 ment with dilute acid. Besides the igneous particles, the residue 

 contained yellowish casts of the interior of the foraminifera and 

 other organisms l and a little ferruginous dust. 



The limestone (I, 283 Q) from the quarries south-east of the 

 city contains about 6'5 or 7 per cent, of material insoluble in 

 dilute acid. A large proportion of this consists of casts of 

 organisms. The inorganic portion of the residue includes quartz 

 usually angular, occasionally rounded, rarely idiomorphic ; a basic 

 tri clinic felspar, which from its optical properties in thin sections 

 and cleavage-plates appears to be labradorite or bytownite, though 

 a few flakes of oligoclase occur ; rounded augite ; and greenish 

 decomposition-products. All these, with the possible exception of 

 the quartz, appear to be derived from the basic igneous rocks which 

 form the main mass of the outer hills of Girnar. The angular 

 quartz may either represent secondary quartz from the same rocks, 

 or may be derived from the quartz-bearing rocks which are intru- 

 sive in them. It is, however, improbable that the latter contribute 

 much, as their quartz occurs usually in idiomorphic crystals or 

 lenticular blebs. The rounded quartz probably comes from, a 

 distance. A thin section (II) of the limestone in the neighbour- 

 hood of the Uparikot shows material of igneous origin, similar in 

 character though perhaps rather less in amount. A specimen 

 (III, 105 A) from the exposure near Khalilpur, mentioned on p. 562, 

 contains about 12.j per cent, of residue insoluble in dilute acid. 2 

 The particles of igneous origin obtained were found to be, in the 

 first place, plagioclase and rounded augite similar to those in speci- 

 men I, as well as minute fragments of basaltic matrix ; all of which 

 were probably derived from the basic rocks already referred to, though 

 some may have come from the gabbro higher up the course of the 

 river ; secondly, idiomorphic quartz and a triclinic felspar, whose 

 optical properties place it near oligoclase, which seems to be derived 

 from a quartz-keratophyre intrusive into the basic rocks, exposures 

 of which are now found on the northern side of the Sonrakhi gorge. 

 Small particles apparently forming part of the groundmass of the 

 same rock also occurred. A fair amount of rounded and polished 

 quartz as well as angular quartz were likewise found in the 

 residue. 



When first quarried the limestone is rather soft, but it soon 

 hardens on exposure. It is very durable, and in great request for 

 building. For this purpose it is cut into flat rectangular blocks, 

 the larger faces of which follow the planes of lamination. It has 

 been carved in situ into various figures and excavated to form 



1 The material forming similar casts in other ' miliolites ' was considered 

 bv Carter [3] p. 170, and f4] A p. 34, B p. 568, to be identical with the 

 molluskite of Mantell [47, 48, & 50]; but see [5] A p. 313 &B p. 756, 

 where he describes it as yellow ochre. 



2 In one determination as much as 25 per cent, was obtained ; but the 

 material treated appears to have included a broken-up felspar-crystal, which 

 constituted the greater part of the undissolved residue. 



