HALF AN HOUR WITH SPONGES. 69 



such as we may see intersecting and alternating in 

 any old chalk quarry. The spongeous origin of the 

 greater part of such flints is now regarded as more 

 or less settled. You can hardly chip off a thin flake, 

 but you find it crowded with spicules, and with the 

 internal casts of the same species of foraminifera as 

 are to be found in the pure chalk. Flint seems to 

 be forming in this manner now, especially in the 

 deeper parts of the sea. The casts of recent fora- 

 minifera and corals have been repeatedly dredged 

 up, to show that the process which subserved such 

 a wonderful end in the cretaceous period, as well as 

 when the chert beds of the older limestones were 

 formed, is still silently going on. Surely we may 

 say of these sponges, as Montgomery, in his " Pelican 

 Island," did of the coral. 



"Slime their material, but the slime was turned 

 To adamant by their petrific touch ; 

 Frail were their frames, ephemeral their lives 

 Their masonry imperishable. All 

 Life's needful functions, food, exertion, rest, 

 By nice economy of Providence, 

 Were overruled to carry on the work 

 Which out of water brought forth solid rock." 



