which form the opposite Walls of Cross-veins. 457 
necessary to occasion the heaves observed at the different 
points :— 
Depth. Heaves observed. = Extent of motion required. 
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Trifling as the actual differences are, their proportion to the 
total amount of the heaves gives them an importance they 
would not have otherwise possessed. 
Here, too, the hypothesis which requires the subsidence of 
the portions of rock included between the branches of the 
cross-course, and also of that between this cross-course and 
Woolf’s, encounters the same incompatible conditions, which 
require for the production of the observed heaves such an ex- 
tent of motion as would have quite obliterated every trace of 
the cross-course, and even closed every fissure which other 
causes might have produced in the same position. 
IV. The configuration of the parts of the same lodes in 
contact with opposite sides of cross-veins. 
The impossibility, with very few exceptions, of restoring 
the continuity of the lodes heaved by the same cross-vein, by 
any one single motion of equal extent in all the cases, naturally 
leads us to examine the configuration of the portions of the 
same lode on opposite sides of the cross-vein, that we may as- 
certain whether they present such a similarity of outline as 
may furnish an argument in this inquiry. 
For, had they been originally connected and continuous, 
and subsequently separated by a transverse fracture accom- 
panied by an elevation or depression of one of the severed 
portions, on delineating the line of dip of both portions where 
they are in contact with the cross-vein, we should expect to 
find that they had a perfectly cr nearly similar outline; al- 
though the direction of any movement they had undergone 
might not allow the corresponding parts to be found at the 
same levels. 
The tables (1—98.) contain sufficient details of the in- 
clinations of all the veins described to furnish us with a close 
approximation to their true dips. Now if the underlie of a 
lode were delineated, and, at successive levels, the observed 
distances of the heaves were marked, and these fixed points 
were united with each other by lines, the two lines (of inclina- 
tion) thus obtained ought to present an uniformity of contour : 
and the parts corresponding in figure should be found at the 
same or at different levels, according to the direction of the 
motion which had affected one or the other portion. 
Pl. LV., figs. 15, 16, 17, 18, 19, 20, present these com- 
