418 Lieut.-Colonel Sykes on a portion of Dukhun. 



taken in supposing it formed the basis of the Western Ghats. Captain Coulthard speaks of it 

 in Sagar*. Major Franklin also noticed it in the trap of Sagar, in lat. 23° 51', and long. 78° 44', 

 at 1933 feet above the sea, as " frequently globular ; the nuclei of the decaying masses, varying in 

 " size from an egg to a large bombshell, and their decomposing concentric lamellae being generally 

 " very thin, and often very numerous "f. 



Dykes. 



I now pass to the basaltic dykes, several of which came under my notice 

 in different parts of the country. They are all vertical, and I did not observe 

 that they occasioned any disturbance or dislocation in the strata of basalt and 

 amygdaloid, through which they passed. 



Two dykes run obliquely across the valley of Karleh, {S5 miles north-west of Poona), and 

 intersect each other : they are about four feet thick and cut amygdaloidal strata. A prismatic 

 disposition is 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 I 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, 7^ miles north of Poona t- 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 can- 

 tonments 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 400 feet below the crest of the scarp. 

 The path of ascent into the fort is intersected by it, and its prismatic fracture, at right angles to its 

 planes, offers a few available steps in the ascent. It is traceable for about 300 feet in perpen- 

 dicular height. On the top of the 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 advert 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 verti- 

 " cal veins of quartz, or narrow seams of a more compact heavy basalt, which 

 " appears to radiate from centres^." Beyond the continuous trap region of the 

 peninsula. Dr. Voysey notices a basaltic vein in sienite, near the Cavary river 



* •' The base of the hills is invariably broader than the summit ; and if the sides of a hill are 

 " smooth and even, hailed trap, often a concentric lamellar variety will be the principal component 

 " matter, decomposing and decomposed into a predominating workable clay, still showing the 

 " parallel converging layers." — Physical Class, Asiatic Researches, p. 78. 



f Physical Class, Asiatic Researches, p. 30. J See Plate XXVIII. fig. 1. 



§ Malcolm's Central India, Appendix, p. 330, 



