142 ^ioux City Academy of Science and Letters. 



the lowest forms of marine life. But without this doubt- 

 ful one, we have abundant evidence of there having been 

 a teeming life in the oceans, where the Laurentian rocks 

 were laid down. There are immense beds of limestone, 

 great deposits of iron ore and rich mines of graphite. 

 These are all possible only through organic life. Lime- 

 stone is a sedimentary formation, built up of broken and 

 worn shells and corals. Iron is held in solution by the 

 water and is only rendered insoluble and thrown down 

 as a deposit by the chemical action of decaying vegeta- 

 tion. Graphite is only one of the stages through which 

 carbon passes from plant, peat, lignite and coal to graph- 

 ite. All these mineral beds are thus sure indications of an 

 organic life which existed in the times when these rocks 

 were laid down. It is true that there are, all over the 

 earth, small local beds of limestone that are not of ma- 

 rine or organic origin, and that have been deposited by 

 hot springs or by waters holding lime in solution. Stalac- 

 tites and stalagmites are examples of such formations. 

 But such lime deposits are never laid down in even, level 

 strata, but in folded and uneven layers. The limestone 

 deposits of the Laurentian system are true marine sedi- 

 mentary rocks. This formation, the Laurentian, is at 

 least 30,000 feet thick, and was made from still older 

 rocks, which must have been subject to the waves of an 

 ocean more ancient than we can concieve of. All the 

 deposits of this age are found in the northern hemisphere, 

 and most of them very far north. They must have been 

 very much more extensive in area when they became dry 

 land than they now are, for they have furnished most of 

 the materials for the later deposits which lie to the 

 north and south of them. 



There may be secrets of life buried beneath the great 

 ice cap of the south polar regions, but if so they can only 

 be discovered by the men of thousands of years in the 

 future. 



How did life begin? Those who accept literally the 

 story of creation as given in Genesis, believe that all 

 forms of life sprang suddenly into existence at the com- 

 mand of an infinite, all-wise God; that all were created 

 from the dust of the earth; in other words, that by the 



