200 SCIE^'CE SKETCHES. 



So the old Favosites died, or ran away, or were 

 walled up by the younger ones, and new ones 

 filled their places, and the colony thrived for a 

 long while, until it had accumulated a large stock 

 of lime. 



But one day there came a freshet in the Meno- 

 monee River, or in some other river, and piles of 

 dirt and sand and mud were brought down, and all 

 the little Favosites' mouths were filled with it. This 

 they did not like, and so they died ; but we know 

 that the rock-house they were building was not 

 spoiled, for we have it here. But it was tumbled 

 about a good deal in the dirt, and the rolling peb- 

 bles knocked the corners off, and the mud worked 

 into the cracks, and its beautiful color was de- 

 stroyed. There it lay in the mud for ages, till the 

 earth gave a great long heave that raised Wisconsin 

 out of the ocean, and the mud around our little 

 Favosites packed and dried into hard rock and 

 closed it in. So it became part of the dry land, 

 and lay embedded in the rocks for centuries and 

 centuries, while the old-fashioned ferns grew above 

 it, and whispered to it strange stories of what was 

 going on above ground in the land where things 

 were living. 



Then the time of the first fishes came, and the 

 other animals looked in wonder at them, as the 

 Indians looked on Columbus. Some of them were 

 like the little gar-pike of our river here, only 

 much larger, — big as a stove-pipe, and with a crust 

 as hard as a turtle's. Then there were sharks, of 

 strange forms, and some of them had teeth like 

 bowie-knives, with tempers to match. And the 



