1847.] VICARY ON THE GEOLOGICAL STRUCTURE OF SINDE. 345 



from half a mile distance it presents an extraordinary and interesting 

 spectacle. 



A valley opens out on the confined plain at the foot of the hills ; 

 the mouth of the valley, about 500 yards across, seems as if a wall, 

 not unlike the glacis of a fort, had been built from side to side ; a 

 waterfall precipitates itself from above at this distance like a silver 

 thread, the scanty green grass on either side helping to throw it into 

 relief. Close by there are a few scattered trees of Tecoma undulata, 

 which aid in softening the monotony of a scene otherwise naked and 

 barren. On reaching the foot of this natural glacis, where I en- 

 camped, I found that the rock was entirely composed of recent tufa 

 deposited from the stream of water now flowing. Its height is better 

 than 300 feet, and in some places is of great thickness. The only 

 section I could obtain (near the southern margin) gave a depth of 

 from 25 to 30 feet. It appears stratified (if I may use the term), 

 owing to its deposition in successive layers ; the dip on the glacis is 

 from 35° to 45°, accommodating itself to the dip of the nummulitic 

 limestone beneath. The lower and older beds are yellow, the upper 

 and newer white. I found numerous shells imbedded in it, all agree- 

 ing with the species at present existing in the neighbourhood. On 

 the face of the glacis there are five elevated tufaceous walls at irre- 

 gular distances ; each wall varies from a foot or less to five feet in 

 height, with the sides in some places nearly perpendicular ; three of 

 these are prolonged with a height of five feet for some distance 

 into the plain below ; all are channeled above ; four of them are 

 old and deserted beds of the stream ; the fifth is the course of the 

 present stream, which is not larger than an English mill-stream. 

 The water is derived from a hot spring, and is warm at the head of 

 the waterfall, but becomes cool and parts with much calcareous 

 matter in its descent. The deposit is more rapid on the margins of 

 the stream than in its bed, and hence the walls originate. They 

 occasionally break down from floods or other accidental causes, when 

 the stream spreads over the glacis, giving a fresh coat of deposit 

 over a considerable area ; in time the stream again contracts, form- 

 ing its lateral barriers, and eventually, when limited in its channel, 

 becomes elevated in the manner I have attempted to describe. There 

 are several wide fissures in the tufa, formed doubtless at the time of 

 earthquakes : most of them have been filled up with broken tufa 

 and some foreign substances cemented by a new calcareous infiltration. 

 From the head of the waterfall to the hot spring is about 650 yards. 

 The tufa extends to the spring, but thins off gradually, and here 

 rests on the upturned edges of the limestone beneath. The hot 

 spring rises at the foot of one of the numerous transverse clefts which 

 everywhere intersect the Hala Mountains. The water smells of sul- 

 phuretted hydrogen, but has little other mineral flavour, tasting like 

 boiled water, and has a pale green colour. Gaseous bubbles are dis- 

 engaged from the head of the spring along with the abundant dis- 

 charge of water. I have endeavoured to give some idea of this place, 

 because a recent freshwater formation of considerable extent exists, 

 the causes of which are now in operation. In the valleys north and 



