250 PROCEEDINGS OF SECTION C. 
at great depths. J. F. Kemp* instances several mines which 
have sunk to depths of 4000 and 5000 feet, in which the 
water was empounded in the upper levels. In these mines 
the lower levels (below about 500 feet) are practically dry, 
the little water which does permeate through the openings 
in the rocks being removed by evaporation. 
I regret that I am unable in the present paper to discuss 
the many instances of deposits for which there is fairly com- 
plete proof of a meteoric origin, and especially that I can 
give no account of the action of meteoric waters'in effecting 
further concentrations in the upper portions of deposits 
which are already in existence, and which may have originally 
been deposited by other agencies. Quite a new light has 
been thrown on this difficult subject by the investigations of 
American geologists during the last two or three years, and 
the conclusions at which they have arrived promise to be of 
the greatest importance to the mining mei 
*The role of igneous rocks in the formation of veins. Trans- 
actions Am. Inst. Min. Engineers, Feb., 1901. 
TABLE OF CONTENTS. 
PAGE. 
INTRODUCTORY Ee ae ae AG 500 su es 205 
THE METEORIC THEORY ... S aes ot he as 206 
General Be ee Roe 0 ne ANC Soli 206 
The Porosity ‘of Rocks... ae see Ad: 207 
The Motive Forces producing Circulation 40 Ay 50 209 
The Nature and Direction of Under ete Plowage . ite a 211 
General Conclusions act ees Sa at 214 
THE PLUTONIC THEORY ... Soc Sae Sa aes ae 215 
Magmatic Differentiation ; nbs es 215 
Segregations of Titanic Iron ‘Ores i in 1 Gabbro ae 217 
Segregations of Chrome Iron Ore in Peridotite and Ser- 
pentine es “ioe 218 
Segregations of Nickeliferous s Pyrrhotite it in Gabbro dnc 218 
Further Examples of MetallicSegregations Zin cin 220 
Magmatice Extraction... Tie “a moe oe 221 
Contact Metamorphic Deposits Se 222 
Tasmanian Examples of Contact Metamor phic “Deposits 224 
Tin Veins Ay ae 5de a 225 
Ben Lomond (Tas. ) Tin Deposits AoE ade ace 226 
Origin of Tin Veins ; : seu aes ai 229 
Apatite Veins .. ates Se sa nos nee ae 231 
Pyritic Deposits ae va Ee a aitatees Aloe 235 
Geneval is ae 235 
Pyritic Tin Deposits of North Dundas, Tasmania... 238 
Colebrook Pyritic Deposit ait ok bie oa 241 
Barn Bluff Pyritic peur er so ot ah 242 
True Fissure Veins ... a8 50 cia 36 243 
Copper Pyrites Veins ae eos oc aa 40 243 
Silver-Lead Veins ... ao Bay hs Soc So 245 
Gold Quartz Veins Mee PEs se Ae oe 246 
Conclusions if aye ies hop aes See 247 
