m 



The earlier or lower strata appear to be moi*e general 

 and extensive — the fossils of the lowest and simplest 

 forms — those least affected by changing conditions to ex- 

 tend through the longest eras of time. The later strata, 

 as well as the later forms of life, are more local and limited 

 in area and in time, and more complex in character. 



Everything seems to tell ns, now that w^e press the truth 

 so closely to nature, that the rocks have been constantly 

 increasing, as the mobile forms of matter have been de- 

 creasing in volume — the change transpiring under mani- 

 fold conditions, and over shifting and changing areas of 

 the earth's surface, and brought about by the operation of 

 complex natural agencies. Thus uniform laws have neces- 

 sarily produced constant diversity of results, and to human 

 observation, permanent change. 



/m^Mi^ Chanf/ed into Solid Form by Acidification, Alimenta- 



tion and Hespiratioyi. 



In 1774, Lavoisier showed that in the calcination of 

 metals in the air, they acquired as much weight as the air 

 lost. He also found oxygen to be the great agent in com- 

 bustion, acidification, calcination, and respiration. All 

 these processes were analogous, and consisted in the de- 

 composition of atmospheric air, and the fixation of the pure 

 or vital portion of it. The action of dilute acids on metals 

 was also explained by the decomposition of water. 



Notwithstanding an hundred years have passed since 

 this discovery, its real bearing upon the physical history of 

 the earth has never been recognized. . Aerial or liquid 

 oxygen changes its form by acidification as well ^s by cal- 



