Jrom the Tilly Foster Iron Mine. 457 
1, Changes during the epoch of Serpentine formation. 
1. All the common minerals of the ore-bed, excepting the 
magnetite, that is, the chondrodvte, enstatite, hornblende, ripi 
lite, massive chlorite, dolomite, biotite, and also the uncommon 
kinds, apatite and calcite, and two other species yet undetermined, 
occur changed to serpentine. The diversity of the minerals 
thus acted on gives augmented force to the remark in the open- 
ing part of this memoir, that the ore-bed had apparently been 
steeped in heated solutions or vapors; and that the moisture or 
vapors had great dissolving as well as decomposing and recom- 
posing power. 
2. The vast amount of fracturing undergone by the rocks of 
the ore-bed indicates a source for all the heat required for the 
various chemical changes—even if it were over 1,000° F.—in 
the transformation of motion into heat; and if this was the 
source, the epoch of serpentine production and pseudomorphism 
set in immediately upon the fracturing. 
iron ; that from the dolomite is aprie arom or gray-green ; that 
(p. 455), or by t 
substitution of dolomite (p. 456). 
