6i6 



HENRY S. WASHINGTON 



of alkalis remains the same, the new analysis shows a rock 

 relatively richer in potash as compared with soda. 



SiOg 



AI0O3 



Fe.Og 



FeO 



MgO 



CaO 



Na^O 



KgO 



HgO (iio°+). 

 H20(iio°-). 



CO3 



TiO, 



44.40 



19-95 



5-15 



2.77 



1-75 

 8.49 

 6.50 

 8.14 

 1. 17 

 0.24 

 0. 12 

 1-53 



III 



46.06 



10.01 



3-17 

 5.61 

 14.74 

 10.55 

 I-3I 

 5-14 

 1.44 



0-73 



ZrO, 



SO3 

 CI ... 

 MnO. 

 BaO . 

 SrO.. 



Less O = CI 



0.03 



0.37 

 0.06 

 trace 

 0.08 

 o.oi 



100.76 



trace 



0.25 



trace 



III 



0.21 

 0.05 

 0.03 

 trace 

 0.32 

 0.20 



100.01 99-57 

 0.06 0.01 



99-95 



99-56 



I. Arkite, Magnet Cove. Washington, analyst. Sp. gr., 2.770 at 26° C. 

 II. Arkite, Magnet Cove. Noyes, analyst. Williams, op. cit., p. 276. 

 III. Missourite, head of Shonkin Creek, Highwood Mountains, Montana. Hurlbut, 

 analyst. Weed and Pirsson, Ain. Jour. Sci., Vol. II, p. 321, 1896. 



The discrepancy between the two analyses of the leucite 

 rock cannot be explained by the supposition that the specimen 

 analyzed by Noyes carried a larger proportion of pseudo-leucite, 

 since, although the other constituents work out well on this 

 basis, the amount of K^,0 in II is not intermediate between that 

 in I and in Williams' analysis of a pseudo-leucite crystal. It 

 seems to be the case that Noyes' specimen represents a slightly 

 different phase, possibly richer in aegirite, but poorer in diopside 

 and garnet. From my own observations in the field and the 

 specimens collected, I conclude that the specimen of I represents 

 the normal rock more closely than that of II. 



It may be remarked that this supposition is borne out by the 

 fact that analysis I is, in a general way, intermediate between 

 that of the covite and that of the ijolite, given later, while 

 Noyes' is not. This is to be expected in view of the observa- 

 tion noted in my former paper (p. 395), that " while the rela- 

 tions of the ' fine grained ' (shonkinitic) syenite to the leucite- 

 porphyry are uncertain, the former lies apparently outside or 

 above the latter." 



In the absence of discrimination between the two iron oxides 



