183/.] 



Geology of the Deccau. 



355 



generally observable in the fracture, and from one of them I obtained a 

 square prism, which lay at right angles to the walls of the dyke. The 

 texture is compact. The military road running through this valley and 

 down the Bore ghat to Panwell, is frequently crossed by ridges which 

 1 presume to be the outcrops of dykes. A dyke is seen on the southern 

 slope of an insulated hill, near the villages of Bosree and Digghee, 

 seven and a half miles north of Poona*. It is about four feet thick, has 

 a transverse prismatic fracture, is compact, and runs from the bottom 

 to the top of the hill ; but it is not discoverable in the northern slope. 

 It is visible from the cantonments at Poona. A similar dyke occurs in 

 the hill at Ombreh, twenty miles north-north-west of Poona. But the 

 most remarkable dyke runs vertically, from east to west, through the 

 hill fort of Hurreechundurghur. It is first seen, of a thickness of six 

 or seven feet, in the ascent of the mountain on the south-east from 

 Keereshwur, about four-hundred feet below the crest of the scarp. The 

 path of ascent into the fort is intersected by it, and its prismatic frac- 

 ture, at right angles to its planes, offers a few available steps in the 

 ascent. It is traceable for about three-hundred feet in perpendicular 

 height. On the top of a mountain, within the fort, about a mile to the 

 westward, it is discoverable at intervals, cutting through basaltic and 

 amygdaloidal strata. I could not ascertain whether or not it appears 

 in the western scarp of the mountain, the point to which it directs its 

 course being wholly inaccessible. 



The gentlemen whose geological memoirs I have quoted, rarely ad- 

 vert to the subject of trap dykes, and their notices are very brief. 

 Capt. Dangerfield says, " The trap of the southern boundary of Malwa 

 " is much intersected by vertical veins of quartz, or narrow seams of a 

 u more compact heavy basalt, which appears to radiate from cen- 

 " tres,''t Beyond the continuous trap region of the peninsula, Dr. 

 "Voysey notices a basaltic vein in sienite, near the Cavary river at Se- 

 ringapatam, which must have been propelled upwards, as it broke 

 through an oblique seam of hornblende in the sienite, and carried the 

 pieces up above the level of the hornblende vein J. " On the eastern 

 coast," Mr. Calder says, " from Condapilli northward, the granite is 

 " often penetrated and apparently heaved up by injected veins or 

 " masses of trap, and dykes of greenstone."§ 



* See Plate xxxiii. fig. 1. t Malcolm's Central India, Appendix, p. 33o. 

 $ Physical Class, Asiatic Researches, parti, p. 23. I Ibid, part 1. p. 10. 



