240 PROCEEDINGS OF SECTION C. : 
and sandstone. These are often lying nearly horizontally, 
and sometimes form flat anticlinal and synclinal folds. The 
replacement is not so evident in these deposits as at the 
Cornwall Mine, asthe slate is of a more homogeneous nature. 
In one case a band of slate or limestone 20 feet in thickness 
has been completely converted into stanniferous pyrrhotite 
and pyrite for about 300 feet. A remarkable feature about 
the Renison Bell deposits is the complete, or almost complete, 
absence of minerals containing fluorine and boron. Only 
in one instance a small piece of slate was observed which 
contained some fine needles, which I took to be tourmaline. 
Tourmaline porphyry, however, occurs in the vicinity. 
The beautifully-banded structure of some of the North 
Dundas pyritic tin ore might, like the so-called “ Annual 
Rings’ (Jahresringe) of the Rammelsberg deposit, be taken 
by themselves to indicate a sedimentary origm. There is, 
however, distinct evidence that this is not the case. At the 
Renison Bell Mine several of the deposits are confined to 
zones of fissuring, and the metasomatic deposition of the 
pyrites is confined to this zone. In other cases special bands 
of country have been impregnated or completely replaced 
for considerable distances away from the zone of fissuring. 
In the Cornwall and Commonwealth mines, the deposits 
have hardly been sufficiently opened up to afford definite 
evidence of this kind; but here the presence of veins con- 
taining axinite and fluorite is strongly suggestive of 
plutonic action. I believe, however, that in this instance 
the axinite veins were filled after the deposition of the sul- 
phide bodies and their contained tin. A similar conclusion 
has been arrived at by Von Firks with regard to the tour- 
maline in the tin-stone deposits at Mt. Bischoff. From 
microscopic examination he concludes that the process of 
tourmalinisation was subsequent to the process of topazisa- 
tion and the deposition of tin. Thus, it would appear that 
the boric emanations succeed the stannic emanations in 
order of occurrence. That boric emanations, however, may 
occur with, or even before, the deposition of tin, is proved by 
many stanniferous quartz-tourmaline veins and by con- 
tact metamorphism accompanied by tourmalinisation. It 
is evident that this question is one of great complexity. 
Whether the axinite was deposited subsequently to the tin 
or not, however, its presence is strong evidence in favour 
of a plutonic origin of the deposits. For these axinite veins 
are associated with certainly two, and possibly three, separate 
pyritic tin deposits. Whereas in this vicinity they are not 
known apart from pyritic deposits. There is, therefore, 
