CARBON I F B R O U S L I M E 8 T 0 N E S 0 F 1 O W A. 



95 



place in the zoological systems, and fill up gaps in the existing orders of the animal 

 and vegetable kingdoms. 



To think that we, at this day, can demonstrate the structure of the eye of some 

 of these — the most ancient races — and even count the thousand lenses by which 

 light was concentrated to the optic nerve, is truly astonishing ! Is it then sur- 

 prising that it should engage the most earnest attention of the closet philosopher, 

 and awaken the enthusiasm of the enterprising explorer ? 



But palaeontology is not a study of mere curious, scientific inquiry ; it has, also, 

 its practical inferences, and these of the most important character, with their 

 direct, matter-of-fact bearings. In illustration of this view of the subject, permit 

 me, in this connexion, to direct the attention of the reader to Figs. 1, 5, and 6, of 

 Table IV. The fossil corals represented by these engravings are found embedded in 

 the subcarboniferous limestones, and near the top of the series ; always under the 

 true coal-bearing beds ; never above these, or included in them ; and nowhere else. 

 This geological fact holds good not only in Iowa, but throughout the entire range 

 of the subcarboniferous limestones in Indiana, Illinois, Kentucky, and Tennessee. 

 In not a single instance, from the range of the Cumberland Mountains on the east 

 to the interior of Iowa on the west, has a workable bed of coal been discovered in 

 a position beneath the strata of limestone containing these corals. In these organic 

 remains, then, we find the surest, the most unerring guide in the search after this 

 invaluable article of commerce, that warms our houses, that drives our steam- 

 engines, by which we navigate our rivers, lakes, and oceans ; that propels the 

 machinery, by which we weave our fabrics ; that reduces our iron, by which we 

 cultivate our soil, and carry on every conceivable mechanical oj>eration ; that 

 refines our metals, that contributes to the production of both the necessaries and 

 luxuries of life, and by which we transmit intelligence, with the swiftness of light- 

 ning, to stations the most remote. Without the knowledge of this fact, millions of 

 dollars might be expended — have been expended — in fruitless and hopeless mining 

 operations after geological incompatibilities. 



All the figures on Table V., A and B, are equally persistent in their unde- 

 viating geological position, quite below the productive coal-measures, as well as 

 beneath these same coral-bearing beds. 



In stratigraphical palaeontology we have, then, the safest and the most trustworthy 

 index to direct our explorations after mineral treasures in the fossiliferous strata. 



Taken as a whole, these carboniferous limestones are rich in organic relics. The 

 lowest fossiliferous bands, under the oolitic bed, are particularly characterized by 

 remains of bivalve Mollusca, belonging principally to the genera Chonetes, Spirifer, 

 Posidonomya, Arclia, and Allorisma. In consequence of these being chiefly casts, it 

 is rarely possible satisfactorily to determine the species. Associated with these is 

 occasionally found a PhiUijJ-sia. 



The oolitic bed contains Pi'oductus cora, Spirifer striatus, and a gigantic species 

 of Gyroceras, to which (from the locality where found) the name Burlmgtonensis, 

 has been given.* 



See Table X., Fig. 10. 



