412 Expedition to the 



though these are not always manifest without careful exami- 

 nation.* 



This limestone, though rather indistinctly stratified, is 

 marked by horizontal seams, distant one or two ftet, and 

 sometimes more, from each other. Its exposed surfaces be- 

 come somewhat bleached, and rough with small prominen- 

 ces, in which we may often distinctly trace the forms of ani- 

 mal remains. The recent fracture is uneven, distinctly crys- 

 talline, and much like that of many moderately fine grained 

 granites. Careful examination shows, that, in many instances, 

 the most minute particles visible under a lens, have assumed 

 the rhombic form common to the carbonate of lime. These 

 crystalline particles vary greatly in size, and are sometimes 

 half an inch across. In the interior of the casts of animal re- 

 mains they are sometimes less distinct than in parts of the 

 rock where no such remains are discovered. 



These vast beds of sparry limestone consisting almost ex- 

 clusively of deposites from chemical solution, would seem to 

 have been formed during periods when great tranquillity 

 prevailed in the waters of the primeval ocean, and tht-ir al- 

 ternation with limestones of the common earthy variety, and 

 with sandstones embracing fragments rounded by attrition, 

 may be considered as proofs that those periods, whatever 

 may have been their distinguishing peculiarities, alternated 

 with other periods of a different character.* 



This variety of limestone, is perhaps the lowest rock hi- 

 therto noticed, in the country of the Lead Mines, and it may, 

 according to the suggestion of Mr. Schoolcraft, be consi- 

 dered as the basis rock in that district; but as it appears to 

 pass through every intermediate variety into the compact 

 blue limestone, we have hesitated to separate it from that 

 rock, which often overlays the newest sandstones. If this 

 view of the subject be admitted, it results, that we are to 

 consider the whole of that part of the Ozark mountains, 

 which contains the Lead Mines, as belonging to a coal for- 

 mation.! We have met with no primitive rocks in this range 



• The limestone of the Engrlish coal formation is observed to he rendered 

 highly cryata/line, and unjitjor lime, when in theviriniti/ o/trap rock-s.^ It 

 is not improbable that future inquiries may detect rocks of this character 

 among the carboniferous limestones ot the Ozark mountains. 



■f The principal supply of lead used in England, is derived from the 

 rocks of the carboniferous series, they also afford some zinc and copper, 

 but in smaller proportion than the rocks of the transition and primitive 

 \ CoDjbeare and Fhillipps. p. 44d. 



