OBGANIC ORIGIN OF CHALK AND FLINT. 383 



tion to present similar appearances, it is considered that not 

 only is the chalk of organic origin, but that a large pro- 

 portion of the sedimentary strata are derived from the same 

 source, and have passed through the great laboratory of life. 

 This opinion of the vital origin of calcareous strata derives 

 considerable confirmation from the operations of nature. 

 Not only is it found that the coral polyp is rearing reefs and 

 islands from the bosom of the deep, and uniting them into 

 continents ; but on the shores of many of the West India 

 Islands, especially the Bermudas, it is observed, that on the 

 coral formations being exposed to the abrading power of the 

 waves, the sea becomes loaded with calcareous matter, a con- 

 siderable portion of which is drifted to the shores in the 

 state of fine sand, which, being wafted inland by the winds, 

 becomes consolidated by the percolation of water, and the 

 infiltration of carbonate of lime in solution ; so that a white- 

 calcareous stone is formed, of various degrees of hardness, 

 from a coarse friable limestone, to the compact rock em- 

 ployed in constructing the fortifications of the island. 



Lieutenant Nelson* states that the whole of these islands, 

 comprising a hundred and fifty in number, may be called 

 organic formations, as they present one mass of animal 

 remains, in various stages of disintegration. Prom the most 

 compact rock to the loose sand of the shore, the materials 

 are fragments of shells, corals, &c. He therefore ascribes 

 the Bermuda chalk to animal origin, and suggests the 

 extreme probability, that the chalk' of Europe was produced 

 by similar causes. The skeletons of Guadaloupe have been 

 mentioned as being embedded in a limestone rock of the 

 same modern character ; and it is impossible to conceive a. 

 more perfect analogy than is here presented, between the 

 operations of nature at the present moment, and those 

 exhibited in the primeval eras of the earth's history. A series 

 of microscopic observations, has shown that both the ^tabular- 

 and nodular masses of chalk flints are due to the presence 

 of sponges, and that the flints which fill up the cavities of 

 shells and urchins are probably owing to a similar cause. 



FOSSILS OF THE CHALK. These are extremely numerous, 



* Memoir on the Geological Formation of the Bermudas. Transactions of 

 the Geological Society, vol.v. p. 115. 



