248 General Notes. 
ian schists by diabase, in the neighborhood of Weilburg an the 
Lahn, in Hessen, Nassau. In this case the diabase itself has suf- 
fered little alteration, but the schists show to a greater or less degree 
the effects of metamorphic action. The unaltered schists are com- 
posed of quartz, muscovite, hematite and other iron oxides, in 
which are lenticular areas and beds of calcite. Where altered they 
are seen to contain an isotropic groundmass in which are quartz, 
mica and a chloritic mineral. In addition to these the two newly 
formed minerals spinel and andalusite occur. In discussing his re- 
sults, Greim concludes that the diabase supplied sodium and iron to 
the schists, which then underwent the alteration which is supposed 
by Rosenbusch to be characteristic of deep-seated metamorphism. 
—A third excellent paper on contact phenomena is that communi- 
cated by Riidemann. ‘This author has investigated the effect of the 
granite occurring at Reuth, near Gefrees, in the Fichtelgebirge, 
upon the clay slates, phyllites and amphibolites through which it 
cuts. He carefully describes the knotty-schists (Knoten-schiefer), 
the chiastolite and andalusite schists, and the hornfels resulting 
from this action, and reaches some general conclusions relative to 
the way in which an eruptive rock acts in the production-of what 
are commonly known as contact rocks. In both phyllites and clay 
slates the first result of the metamorphic action is the concentration 
of certain of their constituents to form the spots (Knoten). In 
this stage there is little or no other change to be detected. 
The next stage is characterized by the formation of por- 
phyritic crystals, chiastolite in the clay slates of Reuth and other 
localities, and biotite in the case of phyllites (Garbenschiefer). In 
the first case the andalusite owes its origin to the alteration of a 
light green chloritic mineral (griimbelite). In the case of the 
phyllites biotite replaces chlorite. In the third stage the end pro- 
duct of the alteration both of clay slates and phyllites is hornfels. 
This is a crystalline rock composed of quartz, biotite, muscovite 
and andalusite grains. Assuming that these changes in the sedi- 
mentary beds are directly connected with the presence of the large 
granite mass which they surround, the author supposes the earlier 
stages in the alteration to be due to the intense heating to which the 
rocks were subjected at the time of their intrusion by the granite. 
This is shown by the fact that in different beds different contact 
minerals have been produced, while the composition of the altered 
rocks corresponds to that of the corresponding unaltered beds from 
which they were derived. To account for the formation of horn- 
fels, and the minerals so commonly found in it, Riidemann sup- 
poses the energetic action of hot waters upon the constituents of the 
fragmental rocks. The paper is exceedingly well written, and con- 
tains very much of interest.—In connection with the discussion of 
1 Neues Jahrb. f. Min. ete., B. B. v., p. 648.. 
