THE EARTH. 



carbonic acid of the air, but continued to do so, and as fast 

 as it became absorbed and saturated with the calcareous 



FIG. 15. LIMESTONE MADE UP OF ESCR1NITE. 



matter of the soil, swarms of coral-polypi, which were then 

 formed, began to build their habitations in the warm waters 



FIG. 16. LIMESTONE MADE UP OF CORALS (Favosites polyoiorpha). 



of the ocean and rob them of the carbonate of lime which 

 they contained, leaving them capable of absorbing more from 



