AGE AND ORIGIN. 49 
(4) That the number, size, position, length, and arrangement of the 
veins seem independent of the dip of strata, depth of cover, cleavage of 
coal, existing configuration of surface, or other disturbances of the coal 
beds and of local basins or hills. 
(5) Some portions of the coal fields contain them in greater numbers 
and dimensions than others, as also do some coal beds than others, and 
that but few, if any, coal seams are entirely exempt from them within 
the region described. 
(6) That fragments of the vegetation of the period in which they were 
found became incorporated in the vein stuff. 
(7) That metallic minerals have in places formed in and attacked the 
vein material, replacing portions of it and creating nodular and stringy 
ground of excessive hardness. 
(8) That chemical and mechanical reactions have operated in places 
on the vein stuff sufliciently long and of such intensity as to convert it 
into nodular masses of rock in aspect resembling brecciated and varie- 
gated marble. 
(9) That masses of coal embedded in the vein stuff contain the usual 
physical and structural features observable in the seams cut by the veins, 
which proves that such features are older than the clay-veins. 
(10) That the slack-veins antedate the present topography and possess 
a trend having no regard to the courses and distances pursued by the 
clay-veins. 
(11) That joined to, as well as mixed up with, the more prominent clay- 
veins are thinner and more meandering ones, which were evidently pro- 
duced simultaneously with the stronger or leading veins. 
(12) That all clay-veins did not reach up as far as the surface, some 
ending or being nipped in the floor or the roof of the coal bed. 
(13) That the vein-stuff in rare instances was dragged or squeezed into 
the fissures from their walls or lower extremities. 
That a clay-vein has the appearance of coming to an end, either ver- 
tically or laterally, in one place or another, is, of course, no proof that it 
does not in reality open out again farther on, a mere unseen crack con-, 
necting the areas of the vein stuff. 
Whether (a) the clay-veins in the highest coal bed, say, in southwest 
Pennsylvania, descend into the Pittsburg bed or even below it, or whether 
(6) those in the latter bed pass down through the “ Barren” series and 
penetrate the coals, or (¢) whether, on the other hand, the clay-veins in, 
say, the Kittanning coals, now by reason of elevation and erosion near, 
the surface, originally extended up through the whole pile of the Coal 
Measures—in other words, are the roots, as it were, of the veins originally 
