232 Mr. Napier on Mineral Veins and Water- Worn Stoms. 



theories have been advanced. Some suppose that the minerals, which 

 are often combinations of the oxides and sulphurets of metals, have 

 been injected in a fosed state from below. Thus M. Agassiz, speaking of 

 the beds of copper found at Lake Superior, says, — " It must have been of 

 pre-historic origin that the copper has been thrown up in a melted state, as 

 it were boiled up. In places where great quantities have come through, 

 and the rock very compact, it has remained unaltered by other in- 

 fluences ; but where it was thrown up in less quantity, and the rocks not 

 so compact, it has been oxidised and combined with other compounds, as 

 carbonic acid and sulphur, &c. Nearest the metallic beds the copper is 

 found in the state of oxide ; then as we proceed farther, it is found as 

 carbonate and sulphuret, and coming to a gi'eater distance, it is all sul- 

 phurets." 



Another theory ascribes the filling of these veins to emanations of 

 mineral matters in the form of vapours, also from the centre, analogous 

 to the vapours given ofi" from volcanoes, this hypothesis being supported 

 by the fact that metals having analogous properties of sublimating, are 

 often found together. A third, that water holding minerals in solution 

 has passed into the crack, or fissure, and the water having evaporated, 

 has left the mineral ; or that the minerals have been crystallized from 

 their solution, by a galvanic, or electric current. 



It is not my intention to discuss these theories in the present paper. 

 It is sufficient to say, that there is much to be said both in favour, and 

 against each, and many practical difiiculties stand in the way of their 

 adoption. There is, probably, no subject connected with the physical 

 sciences, where the theories of the scientific observer, and the opinions of 

 practical men are so universally opposed, as upon the origin of the filling 

 of mineral veins. And although the practical miner may not be the best 

 authority upon the causes which are, or have been, at work, to till the 

 veins which he may be engaged in emptying; nevertheless, we have 

 always found that the observations of intelligent working-men are 

 worthy of some attention, and should not be thrown overboard in order 

 to clear the way for the establishing of some favourite theory, until they 

 have been subjected to a rigid scrutiny, and proved to be useless. 



An opinion prevails amongst miners, that minerals grow, from observ- 

 ing them eflBiorescing, or crystallizing, from the sides of the rocks ; and, 

 also, that certain veins have been known to become richer in metal, in 

 the course of years, either by the metal increasing, or the matrix 

 decreasing. I will here transcribe the opinion of a practical mining 

 engineer, Mr. Evan Hopkins, who supposes that not only the veins have 

 been filled, but that the crack or fissure, in the rock, is the result of a 

 magnetic action. 



"Numerous instances may be mentioned, where old workings have 

 been partially filled with a fresh crop of minerals; and also where 

 minerals have been decomposed, and disappeared. 



These chemical actions, governed by the subterranean polar currents. 



