1843.] Memoir on Indian Earthquakes. 1053* 



change of composition or form. The large volcanoes of Chedooba are 

 four in number: they are detached mounds rather than cones, varying 

 from 100 to 1,000 feet above the level of the sea, composed of a stiff 

 grey clay, with large quantities of singular fragments of stone; their 

 sides much cut up by the effects of rain ; their summits quite bare, and 

 from 240 to 250 yards in diameter : on these are disposed cones of stiff 

 clay from a few inches to four feet in height, and the same variety of 

 dimensions in diameter. These are hard on the outside, but filled half 

 way up with a thick, well mixed mud, which every now and then 

 exudes from a hole at the side or summit, at the bursting of a bubble 

 of gas which takes place every three or four minutes. There are two 

 other volcanoes of small dimensions, and but little elevation above the 

 plains where they are found to exist; they are composed of the same 

 soil of mud emitting large bubbles of gas : and besides, there are two 

 spots where water alone is brought up by the gas. In all these the 

 water or mud is salt, and their number, with the four petroleum wells 

 which are in constant ebullition with gaseous exhalations, seem to ex- 

 hibit the agent as powerfully and extensively at work throughout the 

 island. The minor volcanic vents seldom exhibit any change: the 

 larger ones when in eruption, which generally takes place during the 

 rains, either throw forth to a considerable height accompanied by 

 flame, fluid mud which spreads over a certain extent on the surface 

 affected boils with the escapement of gas, being too consistent to flow, 

 or be thrown up. The angular fragments of stone mixed with the 

 mud are clearly torn from the strata, through which the vent is forced, 

 and small portions of copper ore (? more probably sulphuret of iron) 

 are found attached to them. 



" Besides the volcanoes seen, one was described as existing under 

 water on what is now a reef N. W. of Flat Island, and which a few 

 years since gave forth flame when in eruption. But independent of 

 such direct evidence, a new examination of many of the reefs would 

 convince us of the fact of the bed of the sea having been equally affect- 

 ed with the surface of the land. 



" I was informed by a native, that the extensive new plain on the N. 

 W. part of the island, which was raised out of the sea about 90 years 

 ago, was only then acquiring its first covering of grass when he visited 

 it 1 5 years after its elevation. 



" The Island of Chedooba measures 151 miles in length ; viz. from 18° 

 40' to 18° 55' 30" N. latitude and 17 miles in width; viz. from 93° 30' 

 to 93° 47' E. longitude, and shews on the map as a square, the South- 

 west angle of which has been reduced with its dependency of Flat Is- 

 land on the South coast ; it covers an area of about 200 square miles. 

 Its general appearance is that of a fertile, well-wooded island of mo- 

 derate height and irregular outline. A band of level plain but little 

 raised above the sea, extends around its coasts, of far greater width on 

 the East than on the West. Within this lie irregular, low, undulating 

 hills, varying in height from 50 to 500 feet, enclosing several higher 



7 d* 



