Page:Madras Journal of Literature and Science, series 1, volume 6 (1837).djvu/380

354 zontal basaltic commas. 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 sections, 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 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 lamellæ being generally very thin, and often very numerous."

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 it