ORIGIN AND MODE OF OCCURRENCE OF GOLD-BEARING VEINS. 153 



as we often find them in, and we should moreover expect to find, 

 were this theory correct, that all veins become richer in character 

 the deeper they are worked. I need hardly say this is not universal 

 in the history of our mines. 



Having, however, done away with the igneous injection and 

 sublimation theories, as regards the mode under which the greater- 

 number of mineral lodes have been formed, and having endeavoured 

 to shew their entire inapplicability to the quartz veins of Australasia, 

 I think before seeking to prove that lateral secretion or any other 

 mode is best applicable to auriferous lodes, I should try to account 

 in the most reasonable way for the forming of these fissures or 

 openings in the rocks, that afterwards became filled with the 

 materials of which the lodes consist, for as I have put injection 

 aside, which considers the containing channels of the veins and 

 lodes to have been formed for the most part about the same time 

 as the injection of the molten vein matter, no other theory, unless 

 it be that of molecular aggregation considers these channels were 

 not already open to some extent before the deposition of the vein 

 matter commenced. 



As true fissure lodes may generally be seen to have been formed 

 upon a fault in the country, the origin of such channels is at once 

 apparent, and can be seen to have been caused by a violent rending of 

 the rocks, making immense cracks in them, generally independent 

 of all natural planes. These cracks may be opened either by 

 tilting of the rock on both or either side, or through the walls 

 sliding on one another, or by a separation of the walls to form a 

 gaping fissure. In the second case the opening for the lode matter 

 may be brought about in the manner shewn in diagram, the 

 irregular line being the crack before it has opened to any 

 extent, and the other diagram showing how it would appear after 

 the walls had slid on each other in opposite directions, and it will 

 be seen by this how veins formed in such a manner must be of 

 irregular thickness. Fig. 10 also gives an illustration of how 

 veins may be formed by the sliding of the walls of fissures on 

 each other, caused by the depression of a portion of the country 

 rock. 



This disturbance of the rock, leading to such fissures being 

 formed, may be due to one of two causes. 1st. A sinking of the 

 strata in a certain place while another portion remained firm 

 would lead to the formation of a system of cracks or fissures. 

 2nd. The intrusion of an igneous rock would act in a similar 

 but more violent manner. 



In both cases fissures would be formed, but in the former the 

 action being possibly slower, the fractures would be most likely 

 to follow natural planes in the country rock, and hence the 

 instances in which we find systems of veins coinciding with and 



