Ko. 161.] 
73 
place furnishes new supplies at successive intervals. This ore is 
deposited, 
1st, From chalybeate mineral-springs; 
2d, From surface waters, containing iron in solution. 
Chalybeate springs contain carbonate of iron in solution, by 
means of the contained carbonic acid. The water, as it flows 
from these springs, is limpid; but at a small distance, losing a part 
of its carbonic acid, a deposition of carbonate of iron begins, giv- 
ing a yellowish tinge to the water, and finally becoming more tur- 
bid, deposites its carbonate of iron on sticks, stones, or leaves, or 
in marshes, pools and ponds, forming in course of time masses of 
considerable extent and thickness. The most careless observer 
must have noticed the iron rust color of water in some marshes, 
and the oily looking scum on its surface. These are indications of 
the formation of bog ore, but it is often in so small quantities as to 
be of no value. 
The deposites from the surface waters, are due to the same cause 
as those from chalybeate springs. All rain water contains car- 
bonic acid, and most soils contain iron. Reddish and yellowish 
soils are colored with iron, and the rain water as it flows over, or 
percolates through them, dissolves the ferruginous matter, and 
bears it in solution to the natural reservoirs of the surface waters. 
If these be ponds or marshes, as the water evaporates, the carbonic 
acid passes off*, while the ferruginous matter precipitates and forms 
bog ore. 
Bog ore is sometimes formed in districts of primitive rocks, by 
the decomposition of those containing iron pyrites, or other ferru- 
ginous minerals which are liable to chemical changes from atmos- 
pherical agencies; but they are far more common in the tertiary 
districts, where the surface is sand with a substratum of clay. 
This ore is not uncommon in many parts of the district, and in 
some places it is so abundant as to make it an object of explora- 
tion. It is dug in some parts of Albany county, and mixed with 
other iron ores in the manufacture of pig iron. 
[Assam. No. 161.] 
10 
