RUBIDGE ON METALLIFEROUS SADDLES. 
285 
When the saddles were traced down to any considerable depth 
the gneiss seemed gradually to lose its laminated character, and 
assume the form of a highly felspathic granite, which lower down 
lost all traces of metal. 
It was evident to me, as I stated at the time, that the deposits of 
ore were due to the surface-actions of water, with what aid from 
electro-magnetic agency I know not. Some of the rocks acted 
strongly on the magnetic needle ; but, as most of them contained iron, 
it might have been owing to that, though all the ores that I tried in 
one or two mines had no such effect. 
I believe that what I then stated still holds good — that at whatever 
depth (and it varied considerably) surface- action ceased, the ore 
disappeared. I mentioned several circumstances to show that even 
the less soluble ores were acted upon by the water of the district, 
and that in the case of Van der Stell's mine the surface of the excava- 
tion has been coated with silicate of copper by permeation through 
the solid gneiss rock since his time, — 1680, 1 believe. 
Your interesting periodical, though ordered through an agent as 
soon as I heard of it, only reached me last month. I find that views 
which I entertained on the nature of granite years ago are fast 
gaining ground on the continent. I wrote about this to members 
and officers of the Geological Society at intervals for several years . 
and, though I did so with the diffidence of one whose position did not 
entitle him to hold an opinion adverse to those of the leaders in science, 
1 believe that I said enough to show that, if the igneous theory of gra- 
nite is abandoned by most geologists ere twenty years elapses, as I 
believe it will be, I was among the first to give it up, and to show 
good reasons for doing so. That if the metamorphic theory was 
true, as applies to gneiss, mica-schist, &c., it was equally true of 
granite, syenite, and greenstone, I felt quite sure in 1855. That clay- 
slate passed quietly into mica-schist, chlorite- schist, gneiss, &c., 
without eruptive rock of any kind, I stated as early. That rocks 
were changed into quartzite by surface-infiltration, I wrote as my 
opinion to Sir R. Murchison in the same year. In 1857 I showed 
good reason to believe that the oversight of this fact had led to great 
error as to the super-position of our strata. Since then I have 
proved that strata set down as primitive and separated from the 
