Capt. Grant on the Geology of Cutch. 317 



plete, the sides of which, about forty feet high, are in the upper part quite 

 perpendicular, and consist of very compact basalt, of a columnar structure ; 

 while the lower ten feet present a talus, composed of volcanic sand, and scorias 

 in very thin laminae. Below the columnar basalt is a bed of a friable variety, 

 three feet in thickness. In some parts the columns are capped with a thin 

 band of ironstone. The interior of this crater is about 80 yards in diameter, 

 and consists of volcanic sand, with imbedded angular fragments of basalt. 

 The most perfect of these craters, or circular spaces, are generally hid from 

 view, being approachable only by the narrow ravine forming the outlet of the 

 watercourse which cuts through them. The basalt varies greatly in texture and 

 general appearance : in some places it is columnar, exceedingly hard and com- 

 pact, in others it contains imbedded crystals of felspar, and it occasionally 

 presents the structure and texture of an amygdaloidal clay. Some varieties 

 also consist of concentric layers of a kind of brittle, clayey substance, inclo- 

 sing a nucleus of hard rock; the whole being imbedded in a mass of clay, 

 which looks as if a number of small roots were entwined about it. All the 

 varieties are frequently found in the same bank or hillock. 



Several other small basins have been blown out in the surrounding table- 

 land, forming inverted cones, about 15 or 20 feet in depth; and are composed 

 of the same materials as those just described. Many of them consist entirely of 

 small, brittle particles, of a pale yellow colour, evidently sulphuric. The clay 

 has, in various places, been burnt into a perfect brick ; and the marls, or sandy 

 clays, are frequently of a beautiful bright purple. Quantities of talc, or mica, 

 lie scattered about, twisted and contorted into a variety of shapes ; and some 

 of the iron ore which covers the surface, appears to have been partially fused, 

 consisting of a spongy, vesicular mass. The whole has the appearance of 

 having been for some time subjected to considerable heat, and then suddenly 

 blown up. The cones and banks of loose volcanic scoriae must be yearly 

 washing away; and it is difficult to conceive, that the walls of solid basalt 

 forming the sides of the craters, can belong to a similar period, having all the 

 appearance and texture of very old basalt ; but it is possible that a recent erup- 

 tion may have taken place in the site of one of a more ancient date, thus pre- 

 senting a mixture of old and recent volcanic products. If it is true, that basalt 

 owes its columnar structure to its cooling slowly under a great pressure, it is 

 impossible that these masses of columnar basalt and the loose cones of scorise 

 can be contemporaneous. 



In the nummulitic marl forming the banks of a river which flows past this 

 patch of blown-up ground, is a stratum of earth containing small nodules or 



2t2 



