Mr. Hopkins’s Abstract of his Memoir on Physical Geology. $63 
theory with which I have been more particularly occupied, 
primary phenomena. The secondary phenomena of faults, 
mineral veins, anticlinal lines, valleys, &c., will be deducible 
from the primary ones just in the same manner in both theo- 
ries, so that nearly the whole of the investigations contained 
in the second section of my memoir will be equally applicable 
to both these theories. 
In that section I have entered, as before intimated, with 
considerable detail into an examination of the secondary phe- 
nomena of elevation, such as anticlinal lines, longitudinal and 
transverse valleys, ejected and injected horizontal beds of trap, 
veins of trap and granite; and also the different phenomena 
of mineral veins, such as the throw and depth of a vein, the 
comparative widths of the best bearing veins and cross courses, 
and the shifts or heaves so frequently recognised at the inter- 
sections of veins. I have also stated reasons for concluding 
that the fissures of mineral veins must have been filled by some 
process of infiltration or segregation (which I profess not further 
to define) from the surrounding mass; and here, viewing this 
point with reference to the subject of joints, I would further 
observe, that the formation of a vein (by which is here meant 
the matter contained in the fissure) might take place along an 
open joint, exactly in the same manner as along a fissure pro- 
duced by any other means. If, therefore, we find veins (such 
as those before alluded to in Cornwall) which cannot be sup- 
posed to originate in the dislocating effects of an elevatory 
force, we should carefully examine how far the directions of 
these veins appear to coincide with those of the leading joints. 
From a hasty inspection of the Cornish veins, I have a strong 
impression that this coincidence will be found to exist in that 
district. It would be important to ascértain this fact by care- 
ful and detailed observation; for, should it be established, it 
will immediately destroy the hypothesis of the contemporaneous 
formation of such veins as a necessary alternative, and at least 
remove one inconceivable process from the speculations of 
geologists, more especially with respect to those who may at 
once be disposed to allow this mode of formation of the Corn- 
ish veins, while they contend for the fact of the mass in which 
they are found being a sedimentary deposit. The difficulty 
of the theory of all similar veins will be reduced by my hy- 
pothesis to that of the formation of joints, a process hard 
enough to conceive, but which has its analogy in that of cry- 
stallization, and must of necessity be recognised. ‘The pro- 
cess of contemporaneous formation of veins, without the pre- 
vious formation of fissures as receptacles for the segregated or 
infiltrated matter, appears to me inconceivable in itself, and 
202: 
