540 STEVENSON— THE FORMATION OF COAL BEDS. [Nov. i, 



the channel-ways in the delta region, which is covered with silt. 

 MacMurdo^^*' pnblished in the Asiatic Journal an account of the 

 India earthquake of 1819. An extract was published in Edinburgh, 

 which has been utilized by Lyell. This earthquake was felt within 

 a radius of 1,000 miles from Bhooj. central in the Indus delta. The 

 previous depth of the shallow eastern arm of the river was only one 

 foot at ebb tide, but it was deepened to 18 feet; the village of 

 Sindree, farther up the stream, was submerged and a lagoon was 

 formed with area of 2,000 square miles. Immediately after the 

 shock an elevated area was observed at the northeast, where pre- 

 viously there had been a level plain. This, the Ullah Bund, is more 

 than 50 miles long, 16 miles wide and has an average height of 10 

 feet above the delta surface. The course of the Indus, as Lyell 

 related, was much unsettled during several years, but in 1826 the 

 river threw a great body of water into the eastern arm, which cut 

 through all artificial dams as well as the Ullah Bund itself. The 

 natural section, thus exposed, showed that the upraised land is of 

 delta material. By 1838, the Sindree lagoon had become almost 

 filled with detritus. 



The area drained by the Po, the great plain of northern Italy, 

 has received voluminous treatment from many geologists. A sum- 

 mary description of the area was given by Collie,^^'' who says that 

 the plain contains 11,000 square miles and that the mountain area, 

 drained by it, is 16,000 square miles. Borings in the plain show that 

 it is covered with approximately horizontal sand, clay and marsh 

 deposits. The river, in spite of the enormous mass of inorganic 

 materials brought down from the mountains, does little toward 

 aggrading the lower channel, as the load is deposited in lakes whence 

 clear water flows. The stream is thoroughly diked from Cremona 

 to the delta marshes, and the dikes are placed at some distance from 

 the channel, enabling the stream, when in flood, to overflow a con- 

 siderable space before reaching them. This intermediate space is 



^^ Captain MacMurdo, " Account of the Earthquake which occurred in 

 India in June, 1819," Edinb. Phil. Journ., Vol. IV., 1821, pp. 106-109; C. 

 Lyell, " Principles of Geology," Vol. II., pp. 98-102. 



."" G. L. Collie. " Basin of the Po River," Bull. Geol. Soc. Amer., Vol. 

 15, 1904, PP- 566-568. 



