456 Mr. Henwood on the Rocks and Veins 
to produce a heave of 36 feet at 22 fathoms deep: the extent 
of such a motion must be about 17:5 fathoms, and the following 
is a comparison of the calculation from such data with the facts 
observed :— 
Distance of heave. 
Depth. Calculated. Observed. 
22 find. atte. SG feeb sus %ae) rm a tay) Oe 
SOc Aimee. AO Maer eas ells lohc, ater Ono uae 
43 wee pitaihctte te (AUT Mocs 3, 0.01 © jel niece Owens 
But theory requires that the branches of the western trawn 
shall be attended by motions successively of greater magni- 
tude as we go westward. But as the two western branches 
have a westerly dip, any subsidence of the mass (horse) of 
granite between them must close and obliterate any openings 
or fissures with a very much smaller extent of motion than is 
requisite for the production of the heaves. These theoretical 
demands are in direct contradiction to each other; and are 
also inconsistent with the prevailing opinions*, that the move- 
ments which caused the heaves were contemporaneous with 
the origin of the fissures now occupied by the cross-veins. 
At 140 fathoms deep, in Wheal Vor, the eastern cross- 
course divides into two veins, which diverge as they descend : 
the lode passes through the wedge-shaped piece of rock in- 
cluded between them, and is heaved by both of them towards 
the left-hand. ‘The fracture here theoretically assumed would 
have permitted this included portion to have subsided. Now, 
at the point of divergence, at 140 fathoms deep, the eastern 
branch of the cross-course is 6 inches, and the western 3 feet, 
in breadth; and the extent which the wedge-shaped mass 
must have subsided from the position it filled before the frac- 
ture, in order that it might leave a vacuity of the requisite 
dimensions, would be about 13°5 feet. 
In order that a motion of 13*5 feet in extent should pro- 
duce a heave of the observed distance of 9 feet at 150 fathoms 
deep, the direction of the movement should be on a line dip- 
ping southward about 57° from the horizon. The following 
is a comparison of the respective distances of the heaves, which, 
according to computation, will be produced by a movement of 
this extent and direction, with the heaves observed :— 
Extent of heave. 
Depth. Calculated. Observed, 
LEOBUS: 4am atn! yO feetar . de aide oo 9 feet. 
10 isteiee: p'sthtee is ats 10. os wielie ip tor aS wae 
1BO beesicvy ateieMe mOsm ss USE eos . 1. ees 
Again, the following shows the distance of the movement 
* Mr. De la Beche, Report, p. 297. 
