88 E. H. L. SCHWARZ 
shaped pellucid quartz grains; these are the remnants of the min- 
erals of the schists digested and almost absorbed. In the irregular 
crystals trains of unaltered mica-flakes pass right across the prisms, 
but in the perfect crystals these ‘‘segregation bands,” as they would 
be called in igneous rocks, have been broken up and digested in the 
main. In many sections, however, little rounded specks occur 
which, under the microscope, appear as little xenoliths of the coun- 
thy, rock. = )iilre andalusite, unable to penetrate and rid itself of 
these remnants, has tied up the indigestible substance in little 
rounded pockets, which may be as much as 1 mm. in diameter. 
The andalusite substance apparently came from the granite, 
because it occupies spaces originally taken up by minerals of vary- 
ing composition; some of the substance of the matrix has undoubt- 
edly contributed to the building up of the andalusite crystals, but 
the part represented by the potash, iron, and magnesium of the 
biotite and by the potash of the muscovite must have been replaced 
by new material. There is further reason for believing that the 
new substance came from the granite, because in Stellenbosch, 
under precisely similar conditions, large feldspar crystals develop. 
Now the granite at George is a muscovite granite and would want 
all the potash for its own minerals, and therefore passed out 
aluminium silicate, but the Stellenbosch granite is a biotite granite 
and therefore could spare the potash, hence it passed out potash 
aluminium silicate. 
THE ACID RESIDUE AFTER ABSORPTION 
It will be evident from an inspection of the photographs accom- 
panying this paper that the sediments have been dissolved by the 
dolerite, and from the analyses given it is apparent that the siliceous 
residue has been removed. Where has it gone to? As there are 
only channels of communication downward, the answer is that the 
siliceous material has gone toward the deeper portions of the earth’s 
crust and there solidified. The granite bosses of the western 
province of Cape Colony represents the siliceous residues; they 
originally had Karroo sediments above them, probably with dolerite 
intrusions. In the Cape Town granite there are dolerite dykes 
associated with the granite, which go right up through the Table 
