3H4 Tlti' Alllri'icdn Geologist. D.-ci-mber, 1891 
.Mr. IJiMiton.* .\. useful section of six feet by this ol)server shows- 
beneath the soil (1) limestone, with crevices filled with limonite; 
(2) limestone softened and decomposed, with crevices containing^ 
more limonite than No. 1 ; (H) meshwork of limonite almost com- 
pletely replacing the limestone, and including resiihial ochre and 
fine sand; (4) complete replacement of limestone by honeycomb- 
ore. Reticulation of limestone by limonite is seen to be pro- 
gressive downwards until no remnants of limestone are left except 
in the form of insoluble residues occupying druses. These afford 
some measure of the contraction incidental to replacement. 
Another striking example of the same kind given by Prof. 
Dana, has been referred to in the memoir, of which the present 
pages are b}' way of continuation, namely, in the Cone ore-bank 
at West StockV)ridge, Mass.f Tts descrii)ti(>ii l>y this observer is- 
as follows: 
■Several layers had liecome wholly replaced by pure limonite, 
and one of these so changed was a yard thick. Some surfaces 
of the limestone were intersected by cracks, making areas three 
to six inches across, as represented in the figure ; each crack hav- 
ing a border of limonite either side, an inch or so wide. " + 
The same authority is cited by Mr. Prime for direct replace-' 
ment of limestone by siderite ultimately weathered to limonite, 
nameh', at Richmond. Mass.?; This occurrence, like others ob- 
served by Prime at Balliets ore-bank near Allentown, Pa., and in 
another ore-bank near llellertown, both in close relation to the 
Calciferous limestone and schists, is, as concluded by him, an in- 
stance of • -alteration of the limestone to carbonate of iron parti- 
cle by particle, or so to term it, a pseudomorph by replacement. "" 
The same writer attributes the limonites of the Calciferous lime- 
stone and schists in a general way, to alteration of ferrous car- 
bonate produced by reaction of ferrous sulphate with calcic car- 
bonate, both diffused and massive. 
Remnants of notably pyritous material have been observed in 
many of the limonite workings of the Green mountain belt of 
Lower Silurian limestones and their southern extension, especially 
*Hep. Tenth Census xv, 188(5, 275. 
tSee Am. Jour, of So, xLrr, 1891, p. 234. 
JAm. Jour, of Sc. xiv, 1877, 13G. Several excellent cuts illustrating 
the transition of limestone into iron-ores have been given by Mr. 
Chauvenet, Kep. Tenth Census xv, 188(), 292, 296, 297, 299. 
4j.\ni. Jour. Sc. ix, 187."). 140. 
