28 A. F. Foerste — Clinton Oolitic Iron Ores. 



ods and results of the commission which deduced a standard of 

 length, following a scheme proposed a hundred and thirty 

 years before, and using a nomenclature too much like the 

 former to be original, we seek in vain for a proper recognition 

 of obligation and find in a few lines a mutilated account of 

 Mouton's scheme, while he barely escapes condemnation in 

 some words of faint praise from those who had thought of a uni- 

 versal measure. It is confidently believed that he who was 

 known only as a priest and chorister was the originator of 

 the decimal system of measures based upon geodetic data, and 

 the brilliant century which deserves credit for the inception of 

 a system which now promises to become universal was not the 



EIGHTEENTH but the SEVENTEENTH. 



Art. IV. — On the Clinton Oolitic Iron Ores / by Aug. 



F. Foerste. 



In the Clinton Group districts of the Alleghany Mountains, 

 the Clinton iron ores are often of the variety known as Oolitic. 

 In making sections of these ores I discovered that the oolitic 

 grains characterizing them frequently show the structure of 

 bryozoans, and more evidently fragmental remains of the same. 

 The grains, although rounded, have by no means the spherical 

 character usually found in oolitic concretions, such for instance 

 as occur in the so-called green sands of Cretaceous and Mio- 

 cene age in this country. They evidently vary in size and shape 

 with the character of the species from which they are formed, 

 and with the size of the fragment before becoming waterworn. 



As a rule the iron has replaced the substance of the bryozoan 

 itself ; all the stages between partial and complete replacement 

 may be noticed, the most complete stages being of course 

 found in the purer ores. Usually, corresponding changes are 

 observed in the cement which binds the oolitic grains together 

 into a solid mass. It is evident in these cases that the origin 

 of the oolitic structure is not due to a concretionary segrega- 

 tion of iron particles, but finds its explanation in the gradual 

 replacement of the lime of the fragmental fossil bryozoans, 

 particle after particle, by the iron ore. When the bryozoans 

 themselves have been replaced by iron ore, but the lime cement 

 filling their original cell cavities has been but slightly altered, 

 the sections of these grains under the microscope often pre- 

 sent a very beautiful appearance. 



At other times, especially in cases of bryozoan remains 

 having cells of large size, the reverse is true, the lime of the 

 bryozoans being little altered, while that of the cement once 

 filling its cells, has been replaced by the iron ore. In this case 



