492 LONG PERIODS OF ACCUMULATION. [Ch. XXIV. 



for the sand and coarser particles, pushed along the bottom, it would 

 take, according to the late survey of Messrs. Humphreys and Abbot, 

 more than a million years for the great river to carry down from the 

 continent to the gulf an amount of solid matter equal to that of the 

 rocks above alluded to.* 



The Ganges, according to the data supplied to mo by Mr. Everest 

 and Captain Strachey, conveys so much larger a volume of solid matter 

 annually to the Bay of Bengal, that it might accomplish a similar task 

 in 375,000 years. 



As the lowest of the carboniferous strata of Nova Scotia, like the 

 middle and uppermost, consist of shallow-water beds, the whole vertical 

 subsidence of three miles, at the South Joggins, must have taken place 

 gradually. Even if this depression was brought about in the course 

 of 375,000 years, it may have been accomplished at the average rate 

 of 4 feet in a century, resembling that now experienced in certain 

 countries, where, whether the movement be upward or downward, it 

 is quite insensible to the inhabitants, and only known by scientific 

 inquiry. If, on the other hand, it was brought about in rather more 

 than a million of years according to the other standard before alluded 

 to, the rate would be little more than a foot in a century. The same 

 movement taking place in an upward direction would be sufficient to 

 uplift a portion of the earth's crust to the height of Mont Blanc, or to 

 a vertical elevation of three miles above the level of the sea. 



The delta of the Ganges presents in one respect a striking parallel 

 to the Nova Scotia coal-field, since at Calcutta, at the depth of eight 

 or ten feet from tie surface, the buried stools of trees with their roots 

 attached have been found in digging tanks, indicating an ancient soil 

 now underground ; and, in boring on the same site for an Artesian 

 well, to the depth of 481 feet, other signs of ancient forest-covered 

 lands ancl peaty soils have been observed at several depths, even as far 

 down as 300 feet and more below the level of the sea. As the strata 

 pierced through contained freshwater remains of recent species of plants 

 and animals, they imply a subsidence which has been going on con 

 temporaneously with tbe accumulation of fluviatile mud. 



In the English coal-fields the same association of fresh, or rather 

 brackish-water strata, with marine, in close connection with beds of 

 coal of terrestrial origin, has been frequently recognized. Thus, for 

 example, a deposit near Shrewsbury, probably formed in brackish water, 

 has been described by Sir R. Murchison as the youngest member of 

 the carboniferous series of that district, at the point where the coal- 

 measures are in contact with the Permian or " Lower New Red." It 

 consists of shales and sandstones about 150 feet thick, with coal and 

 traces of plants ; including a bed of limestone varying from 2 to 9 feet 

 in thickness, which is cellular, and resembles some lacustrine limestones 



* Principles of Geology, 9th ed., 1853, p. 273 ; and Antiquity of Man, 3d ed., 

 Appendix D, p. 522. 



