How Chalk is Made 



lessen ; but in tropical regions, and in warm 

 ocean-streams their numbers are legion. Yet, 

 from depths beyond about two miles, the ooze 

 was not brought up. 



One explanation can be given ; and it is that 

 of the strong dissolving power of sea-water. 

 After a depth of about two miles, the delicate 

 little shells fail to resist that power. Once at the 

 bottom, they might be covered up and pre- 

 served ; but they cease to exist en route thither. 



So in this as in many other instances, we see 

 opposite forces at work. The one force is per- 

 petually undoing what the other force is perpetu- 

 ally doing. Innumerable multitudes of living 

 creatures are at work, taking lime from the 

 water, and constructing carbonate-of-lime. But 

 the ocean is ever seeking to re-dissolve that 

 carbonate-of-lime. 



Another difficult question as to the ooze was — 

 whether the shells of which it is mainly made 

 were those of Foraminifera living in the deep 

 sea, far down below the surface, or of Fora- 

 minifera livino: near the surface. Able men took 

 both sides of the discussion, some ascribing the 

 ooze entirely to deep-sea jelly-specks, others 

 ascribing it entirely to surface jelly-specks. 



The question cannot be said yet to have met 

 147 



