398 Scientific Intelligence. 
amount of transportation by flowing waters may have sag 
as the ferrous carbonate is soluble in carbonated waters. At 
quarry near by a body of ore, Zrenton fossils were found, and ok 
over forty rods off occur the Hudson River shales, so ‘that the 
ore in that case is within 300 or 400 feet of the top of the Trenton 
limestone formation; and this ferriferous horizon there extends 
along the strike of the rocks for about forty rods. 
The volume is an especially cpagegn he contribution to the 
subject of limonite-beds and limonite mak J.D. D 
4. Note on the mahng of Limonite ore totes by J. D. Dana. 
—The results of the Pennsylvania geologists accord well with 
those the writer tee obtained from the study of many of the ore- 
its of western New England and the eastern border of New 
ork. As Professor Lesley observes, “ conditions, the changes 
and the results are the same throughou The source is, in both, 
chiefly the limestone of the Lower Slanse, gions the borders of 
which are overlying Hudson River slates. For the sake of ¢ 
e 
arison, the writer here states in brief his own conclusions, ee 
ing details as to facts for another place. 
(1 e iron ore epos sits occur in the limestone near, 
adjoining, either the main belt of slate or schist, or ccbeeatiied 
layers or small flexures of it. 
2) The iron for the ore was ered from the limestone and 
oy to a small extent from the sl 
3) The iron existed in the limestone as carbonate; probably 
as a _carbonate of ca calcium and iron, or of calcium, magnesium 
bury, and at the Leete ore bed in West Sipskerdas, a 
been found sparingly in other ore pits; its limit peed 3 is 
unknown. 
(4) The ferriferous limestone, owing to its iron and its panes 
undergoes rapid oxidation and decay. The iron-carbonate, 
cause of its a oxidizes slowly at surface and in its *ifts3 
et exposure to the weather for two years suffices to make the 
blocks as black externally as sig limonite from the oxidation. 
5) The limestone ledges in view about an ore pit are not fair 
examples of the ferriferous Shake a that has afforded the ore. 
They contain little iron, or none, and resist decay ; while the more 
ferriferous has disappeared through the oxidation process ¢ and the 
dissolving action of passing waters, or all except clay, sand, ete., 
from its aed ies. 
(6) The distribution of the more ferriferous limestone in the 
ordinary limestone is exceedingly irregular, 
patches, large or small, broad or narrow, deep or shallow, con- 
tinuous or interrupted. Toward the kin end of the Amenia 
