PETROGRAPHY. 
93 
Norm of I. Norm of II. 
Or.... 61.72) 37-53) 
Ab. ... 0.52 > 71.69 i f 54-49 
An. ... 9.41; V 16.96 ) 
T / 14-75 83.90 
Lc I ' 19 . 84 I o yy 
i rt i r> c 
Ne.... 13.06 13.06. 
Di 7.98) 
01.... {.97$ 9 ' 95 
if*:::: il'i 3.84 14.13 ^5 4.s s 15.68 
Ap 0.34 0.34 0.92 0.92 
98.88 99-67 
Rest. ... i .42 -74 
100.30 100.41 
Ratios. 
I. II. 
Sal 
ClaSS Fein" =6 ' 5 ' 36 
F 
Order =5-49 1-84 
K 3 0' + Na 2 0' 
Ran s cao^ =4 ' 6s 2 ' 41 
K 2 0' 
Subran 8 N^O' = 2 '3 6 3-32 
The analyses are remarkable for their figures for potash, which are among the 
highest recorded for this constituent. Those of foglianal vicose resemble each other 
closely, the chief difference being in the silica. The analyses in I and III are mark- 
edly similar, the percentages of potash, soda, and ferric and titanic oxides being almost 
duplicates, while those of ferrous oxide, magnesia, and lime do not differ much. 
But in I both silica and alumina are lower by rather more than i per cent, and it is 
due to this, as well as to the fact that the differences in other constituents, while 
slight, all work out in the same classificatory direction, that the rock represented by 
I falls in the dosalane class and the lendofelic order. Examination of the norms 
and ratios shows that both of the specimens of vicose fall well within all the classifi- 
catory divisions, though II is rather close to the border of the lenfelic order, but not 
enough so to be considered transitional. 
Mode. In neither case could the mode be determined satisfactorily by Rosi- 
wal's method, owing to the fine grain, the fabric, and the mineral composition of 
the microgroundmass, though the relative amounts of the phenocrysts could be 
easily estimated, with the results found in the formal description. On the other 
hand, the mode could be calculated from the norm with ease, the usual procedure 
being followed. The results of these calculations of the two rocks are: 
i. ii. 
Soda-orthoclase, Or z Ab a . . 32.0 13.5 
Labradorite, Ab z An 2 1 1 . 6 23.8 
Leucite 40 . 6 44 . 2 
Nephelite none i . 7 
Augite ii. 2 7.9 
I. II. 
Olivine 2.0 4.2 
Magnetite 2.2 3.8 
Apatite 0.3 0.9 
100.0 100. o 
