Correspondence. 393 
the whole area has been described by me as a labradorite rock area, 
the same name as the earlier geologists have used. 
For the purpose of mapping I agree with the American geologists, 
that it would be necessary to have a group name. And where it is 
desirable to have a group name, I cannot find that we have any better 
than anorthosyte, which long ago has been used by the Canadian geol- 
ogists. And if I have proposed no substitute, it is because, I thought, 
that in spite of the objection above mentioned it might be desirable 
to have a practical group name, and then anorthosyte was the most 
fitting. To replace anorthosyte with plagioclasyte is not necessary. 
We should then have two names for the same rocks, and I think the 
petrographical nomenclature is rich enough before. 
For my part I cannot use the name anorthosyte as title of my new 
paper "Die Labradorfelse des westlichen Norwegens II,"' but in the text 
I have called attention to the fact that these rocks might be called 
anorthosytes, because they consist both of labradorite rocks and and- 
esine rocks. I have also used the name anorthosyte in my lectures 
because my studies of the pkgioclase rocks in the areas of Ekersund, 
Bergen and Loften have shown that oligoclase, andesine and bytown- 
ite rocks occur together with the labradorite rocks. These studies 
have also convinced me, that the term anorthosyte has its value in the 
petrographical systematism as a group name for the leucccrate links of 
the gabbro and dioryte families correspondent to the pyroxenytes and 
other melanocrate rocks. And as we on a more exact examination 
divide the pyroxenytes in diallagytes, etc., we also have to divide the 
anorthosytes in oligoclase rocks, andesine rocks, etc. 
The chemical and petrographical character of the different subdi- 
visions of the anorthosytes is rather' well known. The albite and an- 
orthite rocks are very rare, and I have not seen any analysis of them. 
The chemical relation between the other subdivisions can be seen by 
the following analyses, especially of Norwegian rocks, which I know 
from m\' own examinations. 
II. 
57-34 
25.32 
1 . 10 
0.94 
0.25 
7-99 
5-37 
1.23 
I. Oligoclase rock. Ostvaago, Lofoten. (Kolderup: Lofotens og 
Vesteraalens gabbrobergarter. Mit einem Resume in deut- 
scher Sprache. Bergcns Museums Narbog 1898). 
II. Andesine rock. Fosse, Bergen. Will be published in my new 
paper. Die Labradorfelse des westlichen Norwegens II. 
III. Labradorite rock. Ogne, Ekersund. (Kolderup: Die Labra- 
dorfelse des westlichen Norwegens. Bergens Museums Nar- 
bog 1896). 
IV. Bvtownite rock. Beaver bay, Minnesota. (R. Irving: Copper- 
' Bearing Rocks of Minnesota). c.^rl fked kolderup. 
I. 
Si02 .... 
64.98 
AI2O3... 
19-50 
FeoOg. . . 
2.51 
FeO .... 
0.30 
MgO .... 
0.50 
CaO .... 
370 
NaoO.... 
6.09 
K.O..... 
2.01 
III. 
IV. 
28. 36 
1.80 
- 47-25 
31-56 
2.29 
0.31 
0.27 
10.49 
4.82 
0.84 
15-39 
2.52 
0.37 
