Evolution of tJie Earth. 91 



in the bottom of the sea, accumulating century after cen- 

 tury, forming a deposit which, as it increases, will cover 

 and enclose the shells and remains of larger creatures, reach- 

 ing perhaps in time a depth of several hundred feet. Now, 

 if we take a piece of common chalk, and examine it through 

 the microscope, we shall detect shells and the remains of 

 animals very similar to those we found in the ooze. The 

 chalk, indeed, is entirely made up of these organic remains. 

 We know that it is now found in immense cliffs, hundreds 

 of feet in height, at Dover and elsewhere in England, in 

 France and in Sweden, and in other parts of the world. 

 Flint nodules are also formed in chalk-beds, the diatoms 

 which constitute their nuclei separating from the Foramin- 

 ifera and drawing to themselves concretions of silica and 

 iron. Such examples as these offer conclusive evidence to 

 the scientific mind of the fact that immense areas of land, 

 even high cliffs and lofty mountains, were once situated at 

 the bottom of the sea. None but the grossly ignorant 

 would now argue, as it was seriously argued in no very dis- 

 tant period of the past, that God created these semblances 

 of former life where they are now found, and that they af- 

 ford no proper evidence of the long duration of geological 

 periods. It remained for Christian writers and theologians 

 as late as the fifteenth, sixteenth, seventeenth and eight- 

 eenth centuries, and even of the nineteenth century, to 

 soberly propose this absurd hypothesis. The Pagan scholars 

 of olden times had noted the evidence of marine shells 

 on mountain tops and at a distance from the sea, and right- 

 ly concluded that these facts were indicative of former 

 changes in the earth's surface, — that the rocks in which 

 they were found had originally been submerged beneath the 

 ocean. Such was the judgment of scholars like Pythago- 

 ras, Plato, Aristotle, Strabo, Seneca, and Pliny. Our six- 

 teenth century Christians, however, denominated such phe- 

 nomena "sports of nature," or attributed them to "the plas- 

 tic force of nature," and dated them from the original 

 creation of the world. Even Voltaire, who attempted an 

 explanation in accordance with reason, thought that these 

 shells had been left on the mountains by the Crusaders, as 

 they marched to the Holy Land, — being the refuse of their 

 repasts. It took a full century to explode this idea of the 

 -•plastic force of nature," and a century and a half longer 

 to show the absurdity of the hypothesis that they were 



