192 



PROCEEDINGS OF SECTION C. 



oxide and oxides of nickel and cobalt added to the ferrous iron. These 

 recalculated analyses are given in the following table : — 



These analyses have been plotted in the form of a variation 

 diagram (see Plate VII.). 



An examination of this diagram will show that in general the 

 points conform fairly Avell to the curves with certain rather wide 

 departures. A supposition that these departures are possibly due to 

 analytical errors rather than to real variation is supported by the fact 

 that those analyses which would be classed Al or A2 in Washington's 



