.S5S lln Ann ri'Ut II ( i> i>l(i(/isf. D"T.-nil).T, IWII 
lliut wluiU'Vcr coii.sidiMalyli' iJiopoitioii of rciriffroiis iiuitciial was 
ileposited within compass of the Ciiiitoii liiiH'stoiics. was alter- 
nately deposited in the form of siliceous sediments ri'presented 
by interealations of shale. Such intercalations are common in 
Pennsylvania and Virginia. A less theoretical objection rests on 
the fact that the distribution of the (Mintoii iron-ort's clearly <le- 
l)ends on secondary, and wholly adventitious, conditicnis connected 
with topography and environment.* 
The ap|)lication to the Clinton iron-ores of the views discussed 
in the continued and present memoir, falls in with the conclusion 
of Mr. Aug. F. Foerste, pul>lishe(l since the aliove was written. t 
Microscopic sections of Clinton, dyestone oolitic iron-ores froni 
Pennsylvania, Georgia, antl Ohio reveal, according to Mr. Foerste. 
all stages of replacement of calcic carbonate, both cement and 
oolitic granules, by ferric oxide, the granules being fragments of 
Clinton species of water-worn bryozoans. 'In no case, however, 
was anything noticed leading to the opinion that concretionary 
segregation of iron had taken place either around the bryozoan 
fragments or otherwise. Simple replacement of iron-ore was 
the rule, the attack being made first on the exterior parts of the 
grains." According to the same o])server similar occurrences are 
found thnnighout the Clinton belt whei-ever oolitic iron -ores are 
developed. 
1' Rephicemrnt of CurJioin'/'croK-s Jjiiiicsfoiic.-'. 
Upon any theory of epigenesis of siderite. sjjhivrosidi'rite. and 
sideritic limestone, their greater distribution would seem to be 
natural under conditions for their preservation unaltered, such as 
ma}' be recognized in environments where atmospheric air is dis- 
placed by mixtures of hydro-carbon gases and carlioiiic anhycbide. 
as in formations of the Carboniferous period. 
The so-called upper limestone-ore in eastern Kentucky, is. liki' 
the 8ub-carboniferous or lower limestoni'-ore of the sanu' region, 
described by Shaler, a product of alteratio.n of pseudomorphous 
siderite after limestone. This is a reijlacement of u|)per i)arts 
of the Ferriferous limestone di\ iding the Lowei- Coal .^Ieasures. 
and (^o-extensive with the same di\ision of strata in western 
Pennsylvania, West Virginia, eastern Kentucky and southern 
Ohio, where although known under a common designation, it is 
*See Cut. by W. M. Cluuivenet, Report Tenth Census xv, 188G, 396. 
tAm. Jour, of So. .\li, 1^S!I1, 28. 
