434 
THE CARBONIFEROUS VOLCANOES 
BOOK VI 
revealed in the course of mining operations. Valuable seams of coal, iron- 
stone and oil-shale in the Scottisli Carboniferous Limestone and Calciferons 
hiandstone series are extensively worked, and in the underground opera- 
tions many illustrations of former volcanic action have been met with. 
1 he most remarkable instances of the discovery of buried volcanoes have 
occurred in the Didry coal-tield in the 
north of Ayrsliire. In one pit -shaft 
about a mile and a half to the south- 
west of the village of Dairy, a thick- 
ness of 115 fathoms of tuff was passed 
through, and in another pit 90 fathoms 
of similar tuff w’ere suidc into before the 
position of the black-band ironstone of 
that mineral field was reached by driving 
levels through the tuff into the sedi- 
Fio. 146. — Diagram of Imrieil volcanic cone Stiata OUtside of it. Only a 
near Dairy, Ayrsliire. Constructed from sllOl't distance from these thick piles of 
inlormation olitaiucd in mining operations. . . . , . ^ 
, ^ r ■ * , r,. V , , their place is entirely taken up by 
1. Iliirict. Oimestone. 2. CInybanil Ironstone. 3. , t i J 
Biacy-baiui Ironstone. 4. Uorestone Coal, the Ordinary Sedimentary strata of the 
o. Wee Coal. 6. lliglifieW Limestone, land .. i. • mi i 
S. Tliin Limestones, fl. Linn Limestone. 10. tllStl’lCt. ilie W’Orklllcr-planS of the 
voleanic neck and cionii of tuft’. . , ^ ^ . 
mines show the tuff to occur in irregular 
patches and strips, between wdiich the ironstone is workable. From these 
data we perceive that the shafts liave in some eases been sunk directly upon 
the tops of puys of tuff, which w'ere, in one case, nearly 700 feet, and in 
another iu.stance, 540 high' (Fig. 14G). 
It is obvious that from the condition of a completely buried and con- 
cealed cone every stage may be expected to occur up to the deeply worn- 
down neck representing merely the stump of the volcanic column. The 
subjoined diagram (lig. 147) may serve to illustrate this process of gradual 
re-emergence. 
Fra. 14/. — Diagram to illustrate liow Volcanic Necks may be concealed and exposed. 
], Neck, still buried under the succeeding sedimentary accumulations ; 2, Neck uncovered and denuded. 
When, ill the progress of denudation, a volcanic cone began to show 
itself froiii under the cover of removed strata, it would still for a time main- 
tain its connection with the sheets of tuff or of lava which, when active, it 
had erupted. A number of examples of this structure may lie observed in 
tlie liasin of the Firth of Forth, where the degradation of the surface has 
^ E.vpiaiiation of Sheet 22, Geol. Surv. of Scotland, p. 16. 
