METEORITES OF NORTH AMERICA. 309 



The phosphorus was estimated in 1.0450 grams, and the percentage found was: 



P 0.051 



The soluble silicates were determined by treatment with HC1, sp. 1.06. The action was allowed to take place on 

 the water bath and continued but two hours. The acid then decanted off and the operation twice repeated. This 



treatment gave: 



Si0 2 17. 38 



FeO 10.95 



A1 2 3 0. 20 



CaO 0. 14 



MgO : 17.73 



The insoluble silicates were determined after fusion with NaXO^ The alkalies were necessarily determined in a 

 separate portion. Chromite was not present. 



Si0 2 26. 75 



FeO 4.42 



MnO 0. 10(?) 



A1 2 3 2. 27 



CaO 1. 60 



MgO 8. 72 



K 2 (present but not determinable). 



Na 2 0. 44 



The general composition of the portions of the meteorite analyzed, as derived from the combination of the several 

 determinations, is: 



Fe 6.56 



Ni 0.68 



Co 0.034 



S 1.38 



P 0.051 



Si0 2 44. 13 



FeO 15.37 



MnO a 10 (?) 



CaO 1. 74 



MgO 26. 45 



A1 2 3 : 2. 47 



K 2 Trace. 



NajO 0. 44 



99.40 



The mineralogical composition of the meteorite may be approximately calculated from the above summation. 

 The amount of nickel-iron is determined directly; troilite and schreibersite are calculated from the amounts of sulphur 

 and phosphorus found, assuming that schreibersite has the formula Fe,NiP. The soluble silicate is olivine. The 

 insoluble silicates are regarded as enstatite and the feldspathic mineral noted, the amount of alumina found furnishing 

 the basis for the calculation: 



Nickel-iron 4. 59 



Troilite 3. 79 



Schreibersite 0. 34 



Olivine 46.40 



Enstatite 29. 94 



Other insoluble silicates 14. 36 



99.42 



It must be confessed that the last item in the calculation is not wholly satisfactory, the 14.36 per cent of other 

 insoluble silicates not being accounted for in the microscopic examination. It undoubtedly includes the feldspathic 

 constituent and presumably also a portion of the irresolvable matter of the chondrules. A like condition of affairs was 

 noted by Borgstrom in his description of the Shelburne meteorite, which, from a chemical standpoint, this closely 

 resembles. 



The specific gravity of the Modoc stone was determined on two complete individuals, weighing 1,110 and 490 grams, 

 respectively, by a large apparatus constructed on the plan of the beam balance recommended by Penfield in the latest 

 edition of his Brush Determinative Mineralogy. No attempt was made to exhaust the air from the pores, the stone 

 being immersed in water and, with frequent agitations, allowed to remain until no more bubbles were given off . The 

 average of two determinations was 3.54. 



