from the Tilly Foster Iron Mine. 451 
The condition of another portion of one of the specimens is 
shown in fig. 10; it represents a polished surface, four-tenths 
of an inch wide, enlarged about ten times. (To avoid errone- 
. Ha gical 
Sheffield Scientific School of Yale College, the specific gravity 
“The analysis, made on an equal mixture of the green and 
i 41°80 
white, afforded — SiO 
20, 0°95 
FeO 4°65 
Mg 38°55 
i 13°95 
