INDUSTRIAL PROGRESS DURING THE YEAR 1875. ciii 



the adjacent beds of limestone, embedded in which are more- 

 over casts in serpentine of small chambers, single or in 

 groups, having the form and mode of aggregation of glo- 

 bigerina, but with the proper wall of eozoon. These he has 

 provisionally named Archoeospherhia. The eozoon is gen- 

 erally preserved by infiltration with serpentine ; but some 

 specimens in dolomitic limestone have their canals filled 

 with transparent crystalline dolomite, while the skeleton is 

 still pure carbonate of lime. 



In Missouri the published results of the geological survey 

 by Pumpelly and Schmidt have added to our knowledge of 

 the ancient crystalline rocks which rise through the paleo- 

 zoic strata in the southeastern part of the state, and evi- 

 dently formed islands in the paleozoic sea. These eozoic 

 rocks consist in great part of stratified petrosilex, often jas- 

 per-like, and frequently becoming a feldspar- porphyry ; with 

 it are associated argillites and talcose slates, and more rarely 

 layers of quartzite and of crystalline limestone. The rocks 

 have been compared by Hunt with the similar petrosilex-por- 

 phyries of Lake Superior and of the eastern coast of New En- 

 gland, where they form a part of the great Huronian series. 

 They are the iron -bearing rocks of Southeastern Missouri, 

 in which the red oxyd is found either in beds, as at Pilot 

 Knob, or, according to Dr. Schmidt, in great veins, as in the 

 Iron Mountain. The granites of the region apparently break 

 through these ancient crystalline strata. Details are given 

 with regard to the numerous deposits of iron, lead, and cop- 

 per ores in the paleozoic strata, affording important data for 

 a theory of ore-deposits. The lead ores of this region are 

 not confined, as was formerly supposed, to the strata below 

 the Trenton, but are found in the sub-Carboniferous lime- 

 stones and even in the coal-measures. The similar deposits 

 of this ore in the valley of the Upper Mississippi, as is well 

 known, are in a formation just above the Trenton, and the 

 question is now raised whether throughout this wide region 

 the deposition of this metal went on at intervals throughout 

 the whole of the paleozoic period, or whether it was, as sug- 

 gested by Dr. Schmidt, introduced into these various forma- 

 tions at a later date. 



In the lower Carboniferous a deposit of chert, which in 

 some localities is over one hundred feet in thickness, consti- 



