314 



Capt. Grant on the Geology of Cutch 



crystal and chalcedony in all its varieties. The surface of the plains is co- 

 vered with fragments of these minerals, derived from the disintegration of the 

 amygdaloids, which are rapidly affected by exposure to air and water. Some 

 of the sides of the hills are covered with heaps of rock crystal, as if cart-loads 

 had been purposely thrown down. 



AUernation of Basalt with Travertin.— h. very good example of successive eruptions of basalt 

 occurs near the small village of Wurrowsow, on the south-western flanks of the Charwar range. 

 This point must at one period have been a lake, it being now a dead flat, about 44- miles in diameter, 

 and surrounded by low but steep hills, whose surfaces are covered with small fragments of basalt • 

 its general level is about 20 feet above the ground to the east of it. The soil consists of alluvial 

 matter and fine gravel, totally different from the sandy plain by which it is bounded ; but its most 

 interesting feature is the basalt at the eastern outlet or break in the low surrounding hills. This 

 mass of trap consists of perfectly polygonal columns about 25 feet in heio-ht, but broken 

 into lengths, forming a series of regular steps, cut into a horse-shoe shape by a small stream, 

 which discharges itself during the rainy season. The hills that flank it on each side are composed 

 of a base of coarse sandstone capped by an earthy basalt, a dyke of which, 8 or 9 inches wide 

 has, in one spot, penetrated the subjacent sandstone. The following is the section exposed in the 

 liorse-shoe part of the fall. 



_ 



— 



=^ t:^-- 



— — 





^=^ — J — __-.= -= 



m 



U' 



IflflliP 



W<:'i^a^^iy^. 



Rubbly Basalt. 



Crystalline Travertin. 



Friable calcareous stone. 



Travertin. 



Friable Iron-clay. 



Solid Basalt. 

 Friable Basalt. 



Tiie friable basalt forms the base of the fall. Above tlie columns the bed of the small stream 

 consists of a loose, calcareous calc-tufl^. 



This section presents several interesting facts ; as, from the alternation of basalt with the lime- 

 stone or travertin, it is evident, that a considerable time must have elapsed between the igneous 

 eruptions. The variety in the texture of the limestone or travertin may be accounted for by 

 supposing, that the waters under which it was deposited were sometimes perturbed, or rendered 

 muddy by a flood ; but at other seasons clear, when a pure calcareous precipitate would take 

 place. The basalt forming the columns is very hard, compact, of a dark blue colour, and smooth 

 surface ; and it may be traced to some small hills northward of the spot. 



Near this place the surface has been affected in a manner worthy of ob- 

 servation. Every here and there, a small spot, varying in size from 3 to 20 



