176 Mr. D. Forbes's Researches in 



Sulphur .... 37-50 



Iron 49-97 



Nickel 11-17 



Cobalt and copper . traces 



Magnesia .... - 96 



Insoluble matter . 0-24 



99*84 



Subtracting the amount of insoluble matter and magnesia and 

 dividing the loss equally on the remaining constituents, we have 

 the percentage composition as follows : — 



Sulphur . . 37-50 38-01 



Iron . . . 49-97 50-66 



Nickel . . . 11-17 11-33 



98-64 100-00 



Considering the nickel to be present in this mineral in the 

 state of protosulphide (which is probable/Jboth as that compound 

 is known in the mineral kingdom in the pure state as Millerite, 

 and also as, in the Gap mine, Lancaster county, Pennsylvania, 

 Millerite is occasionally found in the nickeliferous pyrrhotine 

 which forms the object of the exploration), the exact state of 

 sulphuration of the iron is still somewhat uncertain ; for whilst 

 some mineralogists have regarded this mineral as being merely 

 a protosulphide of iron in which the iron is in part replaced by 

 the nickel, the larger amount of sulphur shown in this and many 

 other analyses, as well as the strongly magnetic properties of the 

 mineral, appear to indicate the probability of the iron being 

 really present as pyrrhotine or magnetic sulphide of iron (Fe 7 S 8 ). 

 Taking both these views into consideration, the following per- 

 centage composition would approximate to the numbers found 

 experimentally : — 



5FeS + NiS. 5(Fe 7 S 8 ) + NiS. 

 Sulphur . . 36-16 37-18 



Iron . . . 52-73 51-89 



Nickel . . . 11-11 1093 



100-00 100-00 



Some have supposed that these ores maybe a mere mixture of 

 pyrrhotine with more or less Eisennickelkies ; but as this latter 

 species is stated by its discoverer, Scbeerer, to be non-magnetic, 

 a property which he made use of in order to obtain it free from 

 the strongly magnetic nickeliferous pyrrhotine which accompanies 

 it in situ, the Inverary mineral, picked as clean as possible, was 

 pulverized and then treated with a magnet in order to see whether 

 any non-magnetic particles of Eisennickelkies would remain be- 



