402 THE WONDERS OF GEOLOGY. Lect. IV. 



substance, termed molhiskite* The shells, which were 

 empty at the period of their becoming imbedded, had their 



Lign. 95.— Polished slab of Sussex marble. 

 {Composed of Paludince and Cyprides.) 



cavities filled with mud, silt, or other detritus, which has 

 subsequently hardened into clay, marl, limestone, &c. : but 

 those which contained the gelatinous bodies of the snails, 

 are occupied by a mass consisting of carbon, and a large 

 proportion of phosphate of lime. In the polished sec- 

 tions of the marble, this carbonaceous animal matter often 

 appears in black or dark brown spots and veins : and 

 the most beautiful slabs owe their variegated appearance 

 to the contrast produced by the molluskite with the white 

 calcareous spar. Upon examining thin slices of this mar- 

 ble under a slightly magnifying power, many of the shells, 

 and the interstices between them, are seen to be filled up 

 with the cases of Cyprides (Lign. 98). 



• See Medals of Creation, vol. i. p. 431. Geology of the Isle of 

 Wight, p. 248. 



