354 



Geologij of the Deccan* 



[Oct. 



zontal basaltic columns. The hill has been cut away, to form the 

 great military road. In making the escarpment, the balls were met 

 with, and it being impossible to cut through the nuclei in vertical sec- 

 tions, it was either necessary to leave them projecting or to remove 

 them altogether : in the latter case cavities remained equal to the 

 hemispheres of the nuclei ; and the vertical sections display from ten 

 to fifteen concentric layers of friable gray stone,which in some instances 

 I have found to affect the needle. I compared specimens of the nuclei 

 with a mass brought by me from the Solfatara at Naples, and found 

 them quite similar in aspect, colour, hardness, and great weight. This 

 formation excited the attention of those gentlemen who have 

 visited the northern and eastern parts of the great trap region;* 

 but Dr. Voysey was quite mistaken in supposing it formed the basis 

 of the western ghats. Captain Coulthard speaks of it in Sagarf . Major 

 Franklin also noticed it in the trap of Sagar, in lat. 23° 5 1 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 bomb- 

 " shell, and their decomposing concentric lamella? being generally 

 " very thin, and often very numerous." J 



Dykes. — I now pass to the basaltic dykes, several of which came to 

 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 (thirty-five 

 miles north-west of Poona), and intersect each other : they are about 

 four feet thick and cut amygdaloidal strata. A prismatic disposition is 



* Dr. Voysey says, " The nodular wacken or basalt is one of the most common forms 

 " of trap in the extensive districts composed of the rocks of the family south of the 

 " Nermada (Nerbuddah) river. It occurs perpetually in the extensive and lofty range of 

 '*■ mountains (the Gawalghur), situated between the Purna and Tapti rivers, and appears 

 " to form their principal mass. It is found equally abundant throughout the whole of 

 " Berar, part of the provinces of Hyderabad, Beder, and Sholapoor, and appears to form 

 " the basis of the great western range of trap hills which separate the Eonkun fiom the 

 *' interior of the Dukhun."— Physical Class, Asiatic Researches, pp. 126, 189. 



t " The base of the hills is invariably broader than the summit ; and if the sides of a 

 '* hill are smooth and even, balled trap, often a concentric lamellar variety will be the 

 " principal component matter, decomposing and decomposed into a predominating work- 

 V able clay, still showing the parallel converging lay exa."— Physical Class, Asiaik Re* 

 searches, p. 78. 



% Physical Class, Asiatic Researches, p. 30. 



