968 Memoir on Indian Earthquakes. [No. 156. 



building up without altering its centre of gravity; while the waving 

 motion throws it completely out of equilibrium and insures its fall ; 

 the horizontal motion is occasionally destructive, but not so much so 

 by any means as the undulatory. 



3. Miscellaneous effects on the Earth's crust. 



A certain degree and kind of motion of the ground accompany all 

 earthquake shocks, but there are other effects on the earth's crust 

 which are only occasionally observed ; these may now be noticed. 



a. Alterations of level. The most remarkable cases of permanent 

 alteration of level caused by earthquakes recorded in this memoir, 

 are the Arracan and Chittagong earthquakes of 1762, and the Scinde 

 earthquake of 1819. In the former case there is evidence of an up- 

 heavement of a large extent of the eastern coast of the Bay of Ben- 

 gal, while in the latter the Ullah Bund, was suddenly raised and most 

 striking changes occurred in the level of the eastern branch of the 

 Indus. Subsidences of extensive tracts of country accompanied these 

 upheavements: referring to Part II. page 48 and 50, examples of this 

 kind of action will be found in abundance, and in the account of the 

 Scinde earthquake, the formation of a salt water lagoon or marsh of 

 nearly 2,000 square miles in area is noticed. At one part of the 

 eastern branch of the Indus, a depression of level to the extent of 17 

 feet is recorded, while in other parts it varied from 4 to 10 feet. 



b. Rents in the ground with ejection of water and gases. 



A remarkable example of rents in the ground accompanied by the 

 ejection of fetid water occurs in the account of the Cashmere earth- 

 quake of June 1828. Mr. Vigue remarks, " the earth opened in seve- 

 ral places about the city, and fetid water, rather warm, rose rapidly 

 from the clefts and then subsided. 



Another remarkable instance of a great rent occurs in the Calcutta 

 earthquake of 1737? when the English church is said to have sunk 

 bodily into the ground. 



In the Matura earthquake of 1803, extensive fissures were observ- 

 ed in the fields, through which water rose with great violence, and 

 continued flowing from the 1st to 24th of September. 



During the Chittagong earthquake of 1762, many great fissures in 

 the earth occurred, from which water in large quantities rushed with 



