en 
CV + 
fr v N 
DESS: NN å v 
A N:o 1) Igneous Rocks of Sviatoy Noss in Transbaikalia. 49 
No determination of water was carried out in these 
mineral analyses, as the material was too scanty. 
In the calculation of the mode all the other minerals 
were computed as having their theoretical composition except 
the pyroxene and the andradite for which the above analyses 
were used. The epidote and hornblende do not appear in 
- the mode. They were left out of calculation, firstly because 
they are less in quantity than any of the other minerals, and 
secondly because they appear chiefly as inclusions in the 
garnet and in the pyroxene and thus they are, in a way, 
included in the calculated mode also. 
- The following is the result of the calculation, "whose 
method was the general one, elaborated by the authors of 
the »quantitative classification». 
Potash feldspar ........ 24.85 
AMD TGS os ASL. 41.53] 
Anorthite ............. 340: APR 
IPYEO XM Ökad Esa 17.08 
AN UTMOICC i bes one on te 3.98 
HELLA RING 3: sion oa deekiee 179 
22] OEM USSR SA IAEA 1.13 
NagHelbe gosse streets 0.50 
ÖAR LZ törn sas SE 1.11 
100.16 
In the calculation there was left a residue of 1.11 percent 
Si0, which in the above mode was reckoned as quartz. 
Actually no quartz was detected under the microscope in 
spite of much search with convergent light, and it may be 
that the result is due to an accumulation of analytical errors. 
In other respects the result is in good agreement with the 
observation. 
The perthitic feldspar. All the large feldspar 
individuals which give this rock its porphyritic habit consist 
NESTSSn, 
of a regular intergrowth of potash feldspar and sodic plagio- 
clase having the direction of the face M 010 and axis c in 
common. This intergrowth no doubt corresponds with that 
4 
