which form the opposite Walls of Cross-veins. 453 
the effect of such a motion, it is necessary to have particulars 
at different distances, on both sides of the presumed centre. 
These details may be either the directions and distances of 
heaves of different lodes at the same level, or of the same lode 
at several levels. 
It has been already seen (4.) that acurvilinear motion will 
only apply to heaves which progressively increase in magni- 
tude, or to those which are in opposite directions in the same 
vein at different depths, or at the same levels, if the veins be 
different. 
No example of a progressive increase in the extent of a 
heave has been recorded. 
At the United Mines (m), Skues’s flucan heaves 7 lodes, 
which occur in regular sequence towards the right-hand ; 
and 7 others, which also tollow each other in succession, 
towards the left-hand. Of the first seven, 2 dip towards the 
north, 1 is perpendicular, and 4 dip south ; of the second seven, 
1 dips north and 6 dip south. 
As all the lodes on one direction from a given point are 
heaved towards the right-hand, and all those on the other 
towards the left, if this had been occasioned by a rotatory 
motion, the lodes furthest from the neutral point, axis, or 
centre of motion, would have suffered a movement progress- 
ively increasing in extent: consequently the magnitude of 
the heaves ought to increase progressively as they are situated 
further from this axis, or point round which the motion has 
taken place. Now the four right-hand heaves which are 
furthest from this point are respectively 6, 6, 2, and 5 feet in. 
extent, and the four left-hand heaves, similarly situated, are 
two of 6 feet and two of 18 feet each; whilst the lode nearest 
to the point of division on one side is heaved 7 feet, and the 
corresponding one on the other 18 feet. 
Thus the lodes nearest to the neutral point are heaved 
further than those which are most distant—facts in direct 
opposition to the theory. 
III. When the same lode is intersected by two cross-veins, 
namely, a, a', a®, by wa and yz (Pl. IV. fig. 13), if the por- 
tion a' contained between them be the only one moved, any 
motion, excepting one parallel to the dip of the lode a, a', a’, 
must necessarily produce two heaves in opposite directions; 
for no motion of a! can possibly occasion a simple intersection 
by one cross-vein and a heave by the other. 
Of 55 lodes, each traversed by two cross-veins, producing 
110 intersections, there are 90 heaves. Now this hypothesis 
would require that every lode should be heaved in opposite 
directions by the two cross-veins intersecting it; but this is 
