the compounds of chromium. 229 
acted on by the magnet were scrupulously withdrawn. 25 
grains of this pure ore being subjected to analysis, I obtained 
the following constituents : 
Green oxide of chrome 
- 52-95 or 
10 
Peroxide of iron 
- 
29*24 or 
5*52 
Alumina 
- 
12*22 or 
2*30 
White matter - 
- 
3-09 
Water 
- 
0-70 
98*2 
A trace of silica. 
If we exclude the unknown salt, which I have called white 
matter, we see that the ore is a compound of 
2 atoms green oxide of chrome 10 
1 atom peroxide of iron 5 
1 atom alumina - - 2-25 
The very slight excess of iron and alumina, together with 
the trace of silica, were probably derived from some small 
green particles (obviously the gangue of the ore), which I 
could detect with a glass in the portion of the picked ore 
that had not been pounded. It is more than likely that one 
or two of them had got mixed with the pounded ore. 
From the analysis of the Shetland ore, in the table, it seems 
to follow, that it contains no admixture of octahedral iron 
ore ; for in it alone the green oxide of chromium, and the 
per oxide of iron, bear to each other the ratio of 2 to 1. All 
the other specimens subjected to analysis have been contami- 
nated with iron ore. 
