1881 .] 
195 
[Wadsworth. 
pose of mixing it with the Cranston ore. The iron thus produced 
was employed in the casting of cannon. In part at least, “ the can- 
non used in the celebrated Louisburg expedition, in 1745” were 
made from this iron. It seems to have been largely employed in 
the manufacture of charcoal iron in Massachusetts as late as 1834, 
and in 1869 it was extensively shipped to Pennsylvania to be 
mixed with other ores. 
/ 
It was described by Dr. Charles T. Jackson in his report on the 
Geological Survey of Rhode Island in 1840, and later by Prof. 
Robert H. Thurston and others. 
Its association with serpentine was noticed but it does not 
appear that its nature was ever suspected. 
All pronounce it a valuable deposit of iron, and seem to regard 
it as a common form. Dr. Jackson thought it was eruptive and 
gave an analysis as follows. 
Si0 2 23.00 
A1 2 0 3 13.10 
Fe 2 0 3 27.60 
FeO . . . 12.40 
MnO 2.00 
MgO 4.00 
Ti0 2 15.30 
H 2 0 and Loss 2.60 
Total 100.00 
My attention was called to it by some specimens presented to 
me by Mr. H. B. Metcalf in the spring of 1880, and I afterwards 
visited the locality. It did not appear to me to be a common iron 
ore, but rather a basic eruptive rock containing much iron. Sec- 
tions were made from it in order to ascertain its true character. 
It shows microscopically more or less connected spongiform 
masses of magnetite, while the cells and interspaces between the 
magnetite are filled with rounded grains of olivine. The olivine 
is cut through by numerous fissures, which generally show a ferru- 
ginous staining along their sides. Besides this staining the oli- 
vine is comparatively clear and shows little signs of alteration. It 
contains grains of magnitite. This ore, where it has been 
largely quarried, on one side of the hill, shows a porphy- 
