360 



TRANSACTIONS OF THE 



ON THE SCIENCE AND PRACTICE OF MINING. By James 

 Dickson, F. G. S. London; Hon. Mem. G. S. Penn., &c. &c. 



CHAPTER I. 



Whatever may have been the nature of that power 

 which has occasioned those fissures in the strata of the 

 globe which are termed lodes, it appears to have acted 

 at various intervals of time; but to have exerted itself at 

 the same epoch, with few exceptions, in a uniform direc- 

 tion. 



The immediate effect of this power thus set in action, 

 was a separation of the strata in a lineal direction, and a 

 subsidence or displacement of one of the sides of the 

 fissure. 



As a proof of this partial subsidence of the strata, it 

 may be observed, that whereas in simple fissures the two 

 sides, whatever may be the variation in their distance, 

 observe a parallelism and conformity; those of a lode, on 

 the contrary, vary most capriciously in these respects, 

 and are usually in opposition; concavity facing concavity, 

 and convexity fronting convexity. It has also been 

 remarked, that wherever the strata are not perfectly 

 homogeneous, the corresponding beds are invariably 

 found at different levels on the tw^o opposite walls of the 

 lode ; and again the two segments of a lode which has 

 been severed or intersected, are generally found more 

 or less remote from each other, and the ends of the two 

 segments are observed in numerous instances not to cor- 

 respond with each other, at the same level, either in 

 respect to breadth or the nature of their contents. 



The original formation of lodes or veins is a subject 

 which has excited much dispute among geologists; as yet 



