180 GEOLOGY OF THE ISLE OF WIGHT. 



for the most part, are the calcareous shields 

 and chambered shells of the animalcules termed 

 foraminifera ; which swarm in inconceivable num- 

 bers in our present seas, and are daily and hourly 

 contributing to the amount of sediment now 

 forming in the bed of the ocean.* 



The nodules and veins of flint that are so abun- 

 dant in the upper chalk, have probably been 

 produced by the agency of heated waters and 

 vapours. The perfect fluidity of the siliceous 

 matter before its consolidation, is proved not only 

 by the sharp moulds and impressions of shells, &c. 

 retained by the flints, but also by the presence 

 of numerous organic bodies in the substance of 

 the nodular masses, and the silicified condition of 

 the sponges and other zoophytes which swarm 

 in some of the cretaceous strata. 



Although silex or the earth of flint is insoluble 

 in water of the ordinary temperature, its solution 

 readily takes place in vapour heated a little 

 above that of fused cast-iron, as has been 

 proved by direct experiment ;-j- and similar effects 

 are being produced at the present moment by na- 

 tural causes. The siliceous deposits formed by the 



* See " Medals of Creation," Article " Fossil animalcules," p. 21"). 

 t An account of Mr. JeflVrcy's important experiments will be found in the 

 •' Reports of the British Association," for 1840. 



