TRANSACTIONS OF THE SECTIONS. 5/ 



shells and cuttle-fish bones occuv along a level tract which varies from a hundred 

 yards to twenty miles in breadth. The shells have in most cases retained their form 

 and appearance, but in black clay soils they are changed into a clear selenitc or dirty 

 fibrous gypsum, showing crystallization of the latter substance, but retaining enough 

 of their original form and shape to identify their origin. The greater part of the cha- 

 racter of the Coroniandel coast is similar to this. After penetrating through the sand 

 mixed with shells, a deep bed of soft blackish clay is generally found, containing so 

 much water that the foundations of the buildings constructed where it occurs can only 

 be laid on the walls* used for foundations and peculiar to Madras. At Adgar, the 

 small weir, about eight miles from Fort St. George, which forms the limit of the Su- 

 preme Court jurisdiction in that direction, large quantities of recent sea-shells are 

 constantly being dug up for the use of the lime-burners three miles from the shore. 

 These occurred at a depth of from 8 to 12 and 20 feet, under a stratum of red gra- 

 velly soil, the pebbles in which are mostly quartz and angular in form. The whole 

 plain in this direction is considerably raised above the level of the sea, and presents 

 the same geological appearances, the plain between the isolated hills of Amravutty 

 and the sea slopes gradually towards the shore, and has the appearance of an extensive 

 alluvial deposit, from the surface of which the subordinate hills rise like so many 

 islands. The upper bed consists oiregur or black cotton soil, varying from 6 inches 

 to 20 feet in depth, with a subsoil of stiff unctuous clay, a stratum of sand or gravel 

 occasionally intervening. Between Chandole and Chinna Ganjam, a black soil gives 

 place to a belt of sand 8 to la miles in breadth, the whole bearing the appearance of 

 an old sea beach. Along the sea-margin of Western India we find almost everywhere 

 vast expanses of nearly level ground, from 3 to 10 feet above high-water mark, con- 

 sisting exclusively of the shells and gravel such as I have already described, in a loose 

 or cemented state, according to circumstances. When cemented, the material is used 

 extensively as a building-stone, and the greater part of the less substantial houses in 

 Bombay have been constructed from it. It in general abounds in fine fresh water, 

 and forms the ground on which those magnificent cocoa-nut groves which skirt our 

 shores prevail; they extend around the whole of the shores of the Arabian Sea as far 

 as Soonmeani, beyond which my information is imperfect, with the exception always 

 of the vicinage of the debouchures of our great rivers, where the Delta abuts directly 

 on the sea. Around the peninsula of Aden, and along the shoi-es of the Red Sea on 

 both sides, they are peculiarly conspicuous, stretching on the African coast many 

 miles inland. Around Suez there is a vast expanse consisting of shells and gravel, 

 in appearance so fresh and recent, that one might imagine it to have formed the 

 channel of the sea a few months before. Capt. Newbold describes a similar beach as 

 prevalent along many of the shores of the Mediterranean. Returning to the East, the 

 island of Mauritius is belted by an enormous coral reef throughout the whole shore, 

 excepting about 10 miles; this rises from 5 to 15 feet above high-water mark, and is 

 worn in some places into the most fantastic shapes by the surge. The Observatory 

 of Port Louis is built upon a bed of coral 10 feet above high-water mark. Blocks of 

 coral, too vast to be transported b}' any existing agency, are found from 600 to 1300 

 feet inland, cut oflT from the shore by elevated ridges ; and a considerable way in the 

 interior two remarkable headlands of coral, from 20 to 25 feet above the level of the 

 sea, are to be met with in the jungle. The great part of the numberless coral islands 

 which are scattered between the Cape of Good Hope and Ceylon, the Chagos Archi- 

 pelago, the Seychelles, Laccadives and Maldives, appear to have been elevated to their 

 present level by the same upheaval by which the terraces now under consideration 

 have been produced, and I have no doubt abundance of traces of the same thing will be 

 found all along the shores of our Eastern seas. I need not enumerate the numberless 

 examples of old sea-margins to be found all along the shores of England and Scotland, 

 infinitely more familiar, as they must be, to resident geologists than to an exile. 



The theory of subsidence and subsequent upheaval which I have just endeavoured 

 to establish seems alone capable of explaining the production of coral reefs. As the 

 rock on which they rested descended, the zoophytes would naturally work their way 

 upwards to the surface of the sea, on the approach of which their operations are inva- 

 riably discontinued. An upheaval such as I have assumed would bring the surface 

 of our AttoUs to their present level, which they could by no other process have 

 attained. ' 



* Hollow brick cylinders. 



