C. H. Smyth, Jr. — Clinton Iron Ore. 487 



different from them, would also explain the non-existence of 

 dihalides and tetrahalides. 



Assuming that there is a linking group of two halogen 

 atoms in the trihalides, the view advanced, from a considera- 

 tion of the caesium compounds, that the most stable bodies 

 have identical atoms in this group is confirmed by the study of 

 the rubidium and potassium analogues. For, on this assump- 

 tion, all the potassium compounds which could be made con- 

 tain a group of identical atoms, while in the missing rubidium 

 compound they are dissimilar. 



Sheffield Scientific School, March, 1892. 



Aet. LXI. — On the Clinton Iron Ore ; by C. H. Smyth, Je. 



Recent articles discussing the minute structure and the 

 mode of formation of the Clinton iron ore have suggested 

 the publication of certain observations made upon this peculiar 

 deposit, particularly as it appears at the type locality, Clinton, 

 K Y. 



At this point there are three beds of ore, associated with 

 green and gray shales and thin-bedded sandstones sometimes 

 so coarse as to become conglomerates. The character of the 

 sediments and their rapid changes both vertically and laterally, 

 the presence of ripple marks and mud cracks throughout the 

 series, and the abundant fossils, all indicate deposition in shal- 

 low water with constantly shifting conditions. The dip of the 

 strata toward the southwest is so slight as to be hardly notice- 

 able at the exposures. 



The upper bed of ore, locally known as " red flux," varies 

 in thickness from four to six feet, and appears to be made up 

 of pebbles and irregular fragments of organisms coated with 

 ferric oxide, cemented by calcite. Twenty -five feet below this 

 is a two foot bed of workable ore, and one to two feet lower still, 

 the third bed. 



The ore in both of the lower beds is wholly made up of 

 small round grains, usually flattened to lenticular shape, but 

 often nearly spherical, and averaging perhaps l mm in diameter. 

 The entire mass thus presents, aside from its color, the appear- 

 ance of an oolitic limestone. 



After studying numerous thin sections, from various locali- 

 ties, Dr. A. F. Foerste* has concluded that the oolitic appear- 

 ance of the Clinton ore is due to its being made up of rounded 

 fragments of Bryozoa in which the lime is replaced by iron. 



* On the Clinton Oolitic Iron Ores ; this Journal, III, xli, p. 28. 

 Am. Jour. Sci.— Third Series, Vol. XLIII, No. 258.— JraE, 1892. 



