Introduction to Life of the Lakes. 113 



central cavity only remains and this often 

 filled with vapor of water. As these cool, the 

 water settles to the bottom and an air bubble 

 rises to the upper level, making- the water 

 agate so much prized on our coast. 



The rocks made by the sediments of the 

 Pliocene lakes of Oregon are looser, lighter, 

 more porous; the fossil leaves are more mod- 

 ern in style; the animals more like those of 

 to-day, but there were no more quartz filled 

 cavities. 



And now, inasmuch as the aim of this geo- 

 logical narrative is to give, above and beyond 

 the physical changes, the story of the life that 

 the providence of God developed on this is- 

 land, it is needful that we seek to trace the 

 beginnings of these forms that for so long a 

 period were indigenous here in Oregon. 



