384: BRACKISH-WATER AND MARINE STRATA. [Ch. XXIV, 



movement be upward or downward, it is quite insensible to tbe inhabi- 

 tants, and only known by scientific inquiry. If, on the other hand, it 

 was brought about in two millions of years according to the other stan- 

 dard before alluded to, the rate would be only six inches in a century. 

 But 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 the surface the buried stools of trees with their roots attached 

 have been found in digging tanks, indicating an ancient soil now under- 

 ground ; and, in boring on the same site for an Artesian well to the 

 depth of 481 feet, other signs of ancient forest-covered lands and 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 con- 

 tained freshwater remains of recent species of plants and animals, they 

 imply a subsidence which has been going on contemporaneously with the 

 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 carbo- 

 niferous 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 of France and Ger 

 many. It has been traced for 30 miles in a straight line, and can be 

 recognized at still more distant points. The characteristic fossils are a 

 small bivalve, having the form of a Cyclas or Cyrena, also a small ento- 

 mostracan which may be a Cypris, or, if marine, a Cy there (fig. 499), 

 and the microscopic shell of an annelid of an extinct genus called Micro- 

 conchus (fig. 498), allied to Serpula or Spirorbis. 



Fig. 498. Fig. 499. 



a. Microconchtts (Spirorbis) Cypris f inflate (or Cythere T). 



carbonarius. Nat size, Nat size, and magnified. 



and magnified. Murchison.* 

 &. v*r. of same. 



* Silurian System, p. 84. 



