402 Mr. J. A. Phillips on the Connexion of certain 



a. Infiltration. — The material was introduced by aqueous 

 solution. 



b. Aqueous vapours. — The fissures were filled with mineral 

 matter introduced by the agency of steam. 



c. Sublimation. — The substances constituting mineral veins 

 were introduced in a gaseous condition by sublimation. 



d. Injection. — The materials forming veins have, according to 

 this view of the question, been introduced in a state of igneous 

 fusion. 



The formation of veins has been the subject of much specula- 

 tion since the date above referred to ; and various authors have 

 either advanced new theories, or have advocated more or less 

 important modifications of those before promulgated. 



Among the most worthy of consideration may be cited the 

 researches of Mr. R. W. Fox, who, after ascertaining the existence 

 of electric currents in many of the metalliferous veins of Corn- 

 wall, suggested the probability of this force having acted on the 

 various metallic sulphides and chlorides, dissolved in the hot 

 water traversing fissures, in such a way as to determine the pe- 

 culiar mode of their distribution. He has also endeavoured to 

 account for the prevalence of an east and west direction in the 

 principal Cornish lodes by their position at right angles to the 

 earth's magnetism. 



Weighty objections to this theory, however, have been pointed 

 out by W. J. Hen wood, as well as by other experienced miners; and 

 observed facts would indicate that the general direction of veins, 

 in different mining-districts, varies so entirely, that it probably 

 depends rather on lines of fracture than on the action of voltaic 

 currents. In fact Von Beust, in his criticism on Werner's theory 

 (1840), appears to have conclusively demonstrated that the ma- 

 jority of lode-fissures have been produced by volcanic or plutonic 

 agency. 



It is well known that mineral veins are usually found in re- 

 gions in which igneous rocks are abundant, and in situations 

 where they have burst through crystalline or other stratified de- 

 posits. Lodes also more frequently occur in rock-formations of 

 great age than in recent ones ; and certain classes of them (as, 

 for instance, those of oxide of tin) are only found in the oldest 

 rocks. 



Sir Charles Lyell, when speaking of chemical deposits in 

 mineral veins, remarks, "We know that the rents in which ores 

 abound extend downwards to vast depths, where the temperature 

 of the interior of the earth is more elevated. We also know that 

 mineral veins are most metalliferous near the contact of plutonic 

 and stratified formations, especially where the former send veins 

 into the latter — a circumstance which indicates an original proxi- 



