52 
THE GEOLOGIST. 
have attempted to establish this is somewhat defective, but I have 
shown clearly that that on which it is denied is valueless. 
I have already described the interpolation of masses of granite 
among the slate of Cape Town without displacement : this phenomenon 
obtains to a much greater extent in Namaqualand ; groat masses of 
granite, with little if any evidence of stratification, pass gradually into 
gneiss on either side, and, in fact, all round, without change of dip. 
These are called locally "bosses," and their scaling off is remarkable, 
giving them the rounded outline, whence their name. The same 
thing is seen in the change of hornblende-schist into greenstone or 
syenite, with large crystals of hornblende. Numerous instances of 
tiiis occur ; one of the most striking is between Klein Pella and 
Oomsdrift.* 
I have mentioned in a former Paper that the twists of the strata 
in which the copper-ore is deposited occur in gneiss, and when a sec- 
tion is seen on a hill- side no granite is visible, but when worked to 
any considerable depth, the rock loses its laminated character and be- 
comes a felspathic granite or greenstone. A remarkable section was 
observed near Pella : a stream had worked a deep channel in tlie 
rocks ; the edges of the ravine so formed were of well-marked gneiss, 
while the water ran ever a bed of granite without trace of lamina- 
tion, the gneiss preserving the same dip on either side of the ravine. 
Indeed, it appeared to me as if metamorphosis of the rock into felspa- 
thic granite was the normal state below, while the gneissic lamina- 
tion was a superficial indication of the old stratification-planes. 
While on this subject I will mention what appears to me to be a 
singular character of our palaeozoic rocks here. The specimens I 
have sent home will show that all the Devonian fossils here lose 
every trace of their carbonate of lime. They are preserved, often 
very perfectly, in oxide of iron, but in my experience they are seen 
only on the exposed edges of the rocks, be these greatly inclined, as 
at Chatty and Hermansdorp, or only slightly so, as at Coxcomb and 
Jeff'rey's bay. At Chatty I have seen a mass hollowed out in all 
directions by the decay of the encrinites on the edges, while tracing 
the same layer deeper in, it lost all trace of fossils. Prequent repeti- 
tions of this seemed to me to establish it as a rule that the fossils in 
the rock were only exposed by decomposition. Still it may be merely 
accidental. I should be glad to learn whether it is so or not. 
I have stated that in the metallic twists, or saddles, I never saw 
granite in what I could consider the position of an intrusive rock. In 
one of the accessory twists which meet the metallic saddles at various 
angles, and which in section on a flat surface have the appearance of 
a feather, the shaft (a h) of the feather was 
composed of micaceous schist, wdth a few rather 
large crystals of felspar. I have frequently seen 
irregular-shaped patches of mica-schist follow- 
ing neither strike, nor any law that I could per- 
ceive, among the gneiss. Granite occurred in 
the same way in other spots. 
* Drift-ford (of the Orange river). 
