Ge)iei<t>< of Iron - Orcx. — A / mhtiJI . 353 
or lithologic. environment. This I have endeavored to show in a 
recent memoir. By way of continuation (jf that memoir I proceed 
to instance a number of examples illustrating the sjeneral points 
under discussion. 
/. Iron Oris nf tin Snh-in rlioiii finms Jjinu tito)ie of cnsttni 
Ki'iittiiliii. 
Pseudomorph(^us replacement of Sul)-carl»<)nifer()us limestone 
by reddish lirown limonite was ivcoofuizefl l>y Shaler as the mode 
of occurrence and genesis of well-known tlevelopments in eastern 
Kentucky.* The source of iron salts is referred to overlying 
coal-measures, all more or less pyritous, an<l mainly consisting of 
siliceous sediments. Replacement has taken place une(pially. 
apparently as circumstances of environment have varied. This 
has proceeded from without inwaid. that is. from above down- 
ward. Cross-fissures and anfractuosities throughout the mass 
attest contraction. The degree of chemical replacement of 
limestone is in measure of vertical sections of ore-deposits. 
These often rise above the general level of the top of the lime- 
stone, OAving to compai'ativi'ly even shrinkage or chemical erosion 
of the limestone through solvent infiltrations. 
Occasion will be taken to refer to similar occurrences in Ohio 
on the same horizon. 
//. Hi plii(< imiit of loriil-roil,' (/i nnsfoiii). ('iilm. 
In tracing the genesis of some very remarkable isolated bodies 
of mixed lirown and red hematite (turgite) occurring on the south 
coast of the eastern jK*ninsula of Cuba, I descriV)ed them in the 
year ISS-I^ as replacements of limestone in the form of elevated 
and disrupted coral-reef, or only partially indurate(l coralline 
limestone. t The replaced masses of limestone still retain sur- 
faces characteristic of planes of fracture such as may be oli- 
served in costal cliffs of emergecl coral-reef. Indistinct casts of 
corallum partially transformed into licmatite are occasionally 
found, the cells being filled with chlorite. 'I'he condition of form, 
therefore, almost indis}>ensable to proof of i)seudomorphous re- 
placement, is not altogether wanting. 
Some idea of the importance of the .scale on which replace- 
ment in this instance has lieen effected may be formed from the 
fact that the ore-liodies refei'red to su|)pli('il during the year lS!Hi. 
*Geol. Surv. of Ky. 1^76 [ii\ 10. 
t-iwj. Jinir.of >V. \-\vrn (:]), 1884, 410. 
