CHALK STRATA. 103 



action of water), fall to the bottom of the sea and there 

 accumulate in such countless myriads that they form this 

 fine substance, long mistaken for sand, but between which, 

 in reality, there is a marked distinction, the one being 

 formed by the disintegration and grinding-up of rocks, the 

 other the product of organic life ; this, when it has accumu- 

 lated for ages, will, in all probability, form some island or 

 part of a continent, and be the site perhaps of some magni- 

 ficent city, reared upon a foundation of these minute 

 wonders of the deep, whose skeletons will have become con- 

 solidated into a hard and compact stone, of which its houses 

 and churches will, in all probability, be built. 



This is not imagination, as such occurrences haw really 

 taken place all our chalk cliffs and downs constitute 

 part of an immense stratum. Now, every grain of this 

 chalk contains and is made up of thousands of minute shells 

 and corals. ' These chalk downs were once the bed of some 

 ocean which, in all probability, was filled up by their 

 remains. 



What are the railroads and works of men's hands com- 

 pared with this ? Of this chalk (hardened by pressure into 

 limestone) most of our public buildings are constructed, or 

 (changed by pressure and heat into marble) our statues of 

 great men have been carved. What a mockery to choose 

 marble as the medium of rendering our heroes immortal 

 itself the very type of mortality, being formed by the death 

 of millions of creatures. 



In Dr. Carpenter's work on the microscope occurs the 

 following : 



" Thus, when we meet with an extensive stratum of 

 fossilised Diatomacece, in what is now dry land, we can 

 entertain no doubt that this silicious deposit originally 

 accumulated either at the bottom of a fresh- water lake or 

 beneath the waters of the ocean, just as some deposits are 

 formed at the present time, by the production and death of 

 successive generations of these bodies, whose indestructible 

 casings accumulate in the lapse of ages, so as to form 

 layers, whose thickness is only limited by the time during 

 which this process has been in action. 



