364 
A Analysis of augite-syenite from Kangerdluarsuk calculated at 100 per 
cent. with omission of H,O (analysis 16a). 
В Calculated composition of a mixture of augite-syenite (A) and quartz in 
proportion A: $10, = 100: 49°5. 
С Calculated composition of a mixture of augite-syenite (A) with quartz, 
orthoclase, and albite, in proportion A: SiO, : Or : Ab = 100: 675: 
6: 2s 
D Analysis of soda-granite from Kangerdluarsuk calculated at 100 per 
cent. (analysis 2a) 
The calculation shows that the qauntity of quartz, which 
must be dissolved in the augite-syenite if the silica percentage 
is to be raised to the same value as found in the granite, is 
not less than half the weight of the augite-syenite (more exactly 
49°5 per cent., compare column B in the table). This mixture 
of 100 parts of syenite with 49°5 parts of quartz has, however, 
a composition which differs considerably from the actual com- 
position of soda-granite. 
Again, if we calculate the quantities of quartz, albite, and 
orthoclase which must be added to the augite-syenite in order 
to make the percentages of silica, soda, and potash identical 
with the values given by the granite, it will be found that it 
is necessary to add about 70 per cent. of each of these min- 
erals. This proportion of quartz to felspar differs widely from 
that actually found in the sandstone. Moreover, if the result 
of the calculation (given in C) is compared with the composi- 
tion of the soda-graniie (D), it will be seen that there are con- 
siderable differences in the iron oxides and in lime. In this 
case the discrepancy of the iron oxides is of no great interest, 
for the magma might be supposed to have taken up iron 
oxides from the sandstone which is locally rich in hematite, 
and thus the agreement might be made up. With lime, how- 
ever, the difference is more significant, as in spite of the fact 
that the dissolved matter in the calculation is supposed to be 
free from lime, the calculation gives too much of this com- 
pound. The dissolved sandstone may probably have contained 
small quantities of lime bearing felspars. 
