GpaeHi>> of [''"'i-Oi'ex. — Kiinhall. oTl 
thick limestones with thin shales and sandstones. The limestones 
are horizons of siderite and hematite, of which the larger de- 
velopments are irregnlarly distributed within comi)ass of the cal- 
careous strata. Phillips* has given a selection of cuts whicli 
well serve to illustrate the phenomena of indirect replacement of 
limestone by hematite tlirough alterable ferrous carbonate, as 
pointed out by Smyth, f and as attested b}- the presence of fossils, 
identical with those of the limestone, partially converted into 
bnjwn oxide. 
A'. Replace nil lit of M(so::oic Jinwafoiics, Enylmid. 
The iron-ore occupying horizons of estuarine limestoni- of the 
Lower or Bath oolites at the top of the T'pper Lias series in 
Northamptonshire abounds with shells and corals converted into 
ferric hydrate. As animal life could not p(>ssibly have existed in 
waters charged with iron salts to the degree apparently indicated 
by the ore, ^h*. Samuel Sharp concludes that the iron must lutvc 
been introduced ])V infiltration after the deposition of the sedi- 
mentary material, t 
From a mici'oscopic examination. Sorby concluded that Cleve- 
land ironstone of the Middle Lias of Yorkshire has been derived 
partly fnnu mechanical dei)osition, and partly from subsequent 
chemical replacement of <n'iginally deposited calcic carbonate, 
"which probably thus served to collect together from associated 
ferruginous non-calcareous bmls a large [)art of tlu' iron" contained 
in this ore. This is i)articnlarly proved by pscudomorphous 
siderite after aragonite penetrating moUuscus shi'Us originally 
composed of that form of calcic carbonate. I 
Lower Liassic beds of calcareous siderite or feiTo-calcite occur 
iu North Lincolnshire as upper members of a series of limestones 
and shales, and characterized by a great al)undauce of G ri/phncit 
arcuatii. 'IMic ore-series consists of alternatic^ns of unaltered 
ironstone with thin limestones, togetlier aggregating, according 
to a section by .Mr. <{eorge Dove, Ki feet in thickness. The ore, 
as described liy >Ir. I). Adamson. is intercalated with ferriferous 
limestone carrying fnnn H to 1(> per cent, of in^n. || 
*Ore-deposits, 1884, 164. 
tMemoirs Geol. Siirv. of Gr. Britain, Parts T-TV^ pp. IS, 19, 25. 
JAn. Jour. (Jeol. Soc. 1870, 37G; Judd, Mem. Geol. Surv. Gr. Br., IST.l, 
136. 
i?An. Jour. Geol. Soc. 1879, 84. 
Jour. Iron and Steel Inst. 1876, 327. 
