PETROGRAPHY. 119 
Norm 0} 7. Ratios of I. 
Sal 
5 ClaSS ................. F^ =I "79 
3 
p 
Order ................. -- =1.62 
' Rang ................. 
An 
.. n 07 \ 24 
Lc 
| 
Ne 
12 78 \ 39 
38] 
Di 
Ol 
bo 
48 ) 
jj 
o *?6 \ ^ 
2 4 
Ap... 
. I 77 I 
77 
Rest 
99.26 
. O 22 
K 2 O' 
Subrang ............... --, =1.80 
Comparison of this analysis with that of the vesbal type shows that the two are 
remarkably similar, the figures for silica and the alkalis especially being nearly 
duplicates. The ratios, however, show that this type is closer to the border of order 
8 than the other, so close that it should be regarded as transitional between brac- 
cianose where it actually falls, and vesuvose, the homologous subrang in order 8 of 
dosalane. In fact this type was formerly assigned to the subrang of vesuvose* on 
the basis of the incomplete analysis, and the change in position is due to the deter- 
mination of P 2 O S , which, by combining with CaO to form apatite, sets free sufficient 
SiO 2 to change the relative amounts of orthoclase and leucite so that the ratio of 
feldspar to lenads is lenfelic rather than feldolenic. 
Of the two older analyses, that of Haughton (II) most closely resembles the 
latest one, and must be regarded as the more correct. The only differences of note 
are the lower alumina and the very high figure for MnO. This last is undoubtedly 
erroneous, as the amount of this constituent should not exceed 0.20 per cent, and it 
most probably arises from the common analytical mishap of incomplete precipitation 
of alumina, the unprecipitated portion of which is subsequently thrown down with 
the manganese and weighed as such. If this is assumed to be true and the apparent 
amount of MnO is added to that of A1 2 O 3 , the figure for the latter becomes 17.82, 
in close agreement with I. 
Of analysis III little need be said, except that it is undoubtedly incorrect in the 
figures for alkalis, especially potash. The amount shown allows of the formation 
of only 23.1 per cent of leucite, which is much below the proportion which the micro- 
scope shows is present, and would lead to the presence of about 40 per cent of labra- 
dorite, AbjAn 2 , a figure, on the other hand, much in excess of the actual amount. 
Mode. The estimation of the mode of this type is strictly analogous to that of 
the vesbal. While the augite megaphenocrysts could be estimated readily, and the 
microphenocrysts of leucite fairly well, the other constituents did not lend them- 
selves to this method of procedure. On the other hand, the calculation of the mode 
from the norm presents no difficulty, and it is noteworthy that here, as in the vesbal 
type, the silica left available for soda after formation of augite, olivine, leucite, and 
* See reference under the analysis. 
