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Professor Jameson ow connecting Veins. 
I have observed connecting veins ot the same description in 
layers of fibrous gypsum contained in the compact kinds. This 
appearance is represented 'in Fig. 6. Plate III. where a is a mass of 
compact gvpsLim ; h h layers of fibrous gypsum included in it, 
and c c communicating veins. In an extensive limestone quarry 
about a mile to the eastward of Burntisland, there is a fine ex- 
ample of a communicating vein between two beds of a curious 
kind of amygdaloid. The beds are separated from each other 
by numerous strata and beds of bituminous shale, slate-clay, 
clay-ironstone, sandstone, and limestone, but in one place a vein 
of amygdaloid shoots across all these rocks, from the lower to 
the upper bed of amygdaloid. 
How are we to explain the formation of such veins Vol- 
canists say, that communicating veins are proofs of the igneous 
origin of the rocks in which they occur, and that they are formed 
by the spouting of the fluid lava through cracks in the rock, at 
the time when the lower bed was forming, and before the upper 
one was formed. But this hypothesis will not explain the com- 
municating veins of limestone, sandstone and gypsum, because 
these, on the volcanic system, are not lavas. We are inclined to 
view them as illustrations of the simultaneous crystallization of 
rocks of the same formation. 
III. Tiiap-Veins (Whin-Dikes) piiobably of Cotempo-' 
iiANEOus Formation with the Trap-Rocks which they 
TRAVERSE. 
Veins are tabular masses that in general traverse mineral 
strata and beds of different kinds. According to the Volcanic 
or Plutonic hypothesis, they were originally open rents or 
fissures, wide below, but terminating above in the form of a 
wedge, which were afterwards filled from below with melted 
mineral matter, projected from the interior of the earth. The 
Neptunists again maintain, that these fissures and rents were 
wide above, but terminated below, and were filled from above 
with their' mineral contents. The Plutonists adduce as proofs 
of their opinion, veins shut above, and widening below, as 
sometimes happen with metalliferous veins, and also"ivith those 
formed of mountain rocks, such as granite or trap ; while the 
Neptunists offer as illustrations of the truth of their hypothesis, 
VOL. I. NO. I. JUNE 1819. 
K 
