THE GEOLOGV OF WORLI HILL. 



687 



of a dark colour which viewed sideways appear in shape Uke human nail parings. 

 This can well be seen on the compound wall of the Presidency Mill on 

 Fergusson Road where the softer matrix has weathered away leaving the flakv 

 pebbles very promment. These shales, as also the carbonai;eou8 shales previ- 

 ously mentioned contam large pebbles of an igneous rock of a dark colour 

 the largest found by me being about 9 inches in diameter and about 

 3 inches thick. It is very rarely that the pebbles are of a light colour These 

 may be merely concretions. Above the grey deposits there occurs a series of 

 alternate dark and hght shales. These bands are together about four feet thick 

 and seen from a distance are very distinct. In general the dark layers are thin^ 

 ner than the others. To a greater or less extent the sedimentary deposits are 

 charged with carbonate of lime. Iron pyrites is diffused throughout the layers, 

 the more so in the lowest ones. The pyrites probably was the result of the 

 sulphur evolved from the decomposing organic matter acting on the iron in 

 the waters. The frogs seem to have survived through all these changes as their 

 fossils occur even in the highest of the dark shales. The atmospheric influences 

 which made the hard basaltic trap to weather so deep down do not seem to have 

 affected the sedimentary rocks in the least as the moorum is found resting 

 directly on aqueous beds in a good state of preservation. 



The sedimentary strata are extensively cracked, the cracks generally run- 

 ning east to west. They do not exceed a couple of inches in thickness and are 

 geneiaUy filled in with deposits of calcite showing a variety of crystalUsations. 

 It is very rarely that quartz occurs in these fissures but when it does occur it 

 is found in small crystals of a peculiar brilHancy. So far no amorphous quartz 

 has been found. Some portions of the rock have become faulted and some 

 seem to have shded against each other with such a tremendous force as to fuse 

 partially the rock. An evidence of this fact is found in the fairly extensive 

 rounded and polished surfaces with clear strise on them as if a comb had been 

 passed over the semi-melted mass. Wherever faults occur, the layers have 

 taken a sUght bent downwards and were probably fused to some extent at the 

 line of fracture as layers of different materials are found welded together. 



The layers that existed below the lowest frog beaiing band have been broken 

 into and fused by the lower trap coming into contact with them, so that it is 

 not easy to make out the original condition of these beds. This disturbed 

 state of the sedimentary beds gives additional support to the theory that it 

 was the lower trap that forced up these beds, cracking, faulting and sUding 

 them against each other, and if we assume, as we have done, that the upper 

 trap is of a more recent date than the lower one, then it is quite hkely that this 

 heavy weight coming over the aqueous deposits already thrown into unstable 

 equilibrium may have helped in causing further sHps in the beds. But taken 

 all together, these cataclysmic changes were not so tremendous as in Sewri 

 where the aqueous beds have been contorted, fused and jasperised to an 

 extraordinary degree. 



The fresh water beds are being rapidly quarried away as the material broken 

 into metal or rubble commands a ready sale for use in the foundations of build- 

 ings. Being soft and porous it sets better in the mortar than trap metal. 

 Many a house in Bombay wiU have thehonoui- of standing on the fossil remains 

 of the earUest known inhabitant of Bombay-the frog. At the present rate of 

 quarrying and by the contemplated activities of the Gty Improvement rmst 

 in this locaUty, these interesting beds will be completely wiped out at no 



distant date. , j i -^^ tu^ 



III The lower trap is soft and scoriaceous like the trap underlpng the 

 sedimentary beds in the other parts of the City. In general it is ashy grey 

 in colour and resembles very much some of the aqueous deposits. It a 

 only the presence of crystalline texture that differentiates the former. It w 

 quite likely that the character of this trap at least in its upper portions has 



