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that species. In 1827, I discovered a trilobite in one of these 

 iron ore beds. It was called Asaphus Crypturus, by Prof. Green, 

 of Philadelphia, who described it for me at the time. Tentacu- 

 lites also occur in the red iron ore of Little River, one of the 

 beds of this group. The species resembles, in form and size, 

 the magnified drawings of T. minutus, of Hall's Clinton group 

 of New York Fossils. There are Orthocera, and several other, 

 as yet unknown or undescribe'd, molluscs in these ores, and it is 

 difficult to determine their species, since we have only the 

 interior moulds of the shells. They all appear to belong to the 

 Niagara and Clinton groups, of the New York system. 



One of the most curious phenomena presented at these mines, 

 is the magnetic state of some of the ores, while others, not far 

 removed from them, are wholly devoid of magnetism. 



The ore, when deposited at the bottom of the sea, must have 

 been a fine ferruginous mud of per oxide of iron. Since its 

 formation, and probably at the time of its elevation, the most 

 metamorphosed beds were rendered magnetic iron ore, a mixture 

 of the protoxide and peroxide. 



A great number of mines have been opened lately on these 

 ores, and some new beds have been discovered since the original 

 survey was made by Mr. Alger and myself There are two 

 principal and parallel beds, which vary in thickness from six to 

 ten feet, and they have been traced, with certainty, five miles in 

 length, and probably extend to Bear River, near Clements, a 

 distance of thirty or more miles ! Whether these two parallel 

 beds, which are near each other, and dip 80*^, constitute one bed, 

 doubled up like the letter U, or are distinct deposits, we were, in 

 the short time allowed us for our examinations, unable to decide. 

 There are, however, several distinct and separate beds, besides 

 the main ones ; some of them are very compact and magnetic, 

 and others are softer, and are not magnetic ore. The last named 

 variety is seen in the red slates of Little River, and the others 

 near Nictau River, and in very numerous pits and trenches, cut 

 for the purpose of tracing the beds. 



It was found impossible to rely upon the compass needle in 

 surveying the magnetic ore beds, for the needle was astatic over 

 them, and was attracted, even when quite remote from the ore, 



