400 
THE CARBONIFEROUS VOLCANOES 
BOOK VI 
with such materials must have been the scene of prolonged and intermittent 
activity ; successive paroxysms resulting in the clearing out of the hardened 
lava column in the throat of the volcano, and in the rise of fresh lava, with 
abundant ejection of dust and lapilli. 
Necks formed entirely of agglomerate are abundant among the vents 
connected with tlie plateaux. As examples of them I may refer to the series 
already mentioned as fronting the escarpment of the Clyde plateau from 
Strathblane Hills 
Fig. 127. — Section across the vents Duiiigoyn and Dumfoyn, and the edge of the Clyde plateau above 
Strathblane, Stirlingshire, 
1. Upper Old Red Sandstone; 2. Shales, cenient-stones and sandstones (“ Ballagan beds”) ; 3. White sandstone ; 
4. Andesite lavas ; 5. Agglonierute (shown by the dotted portions), traversed by intrusive diabase. /, Fault. D. 
Late dolerite dyke. 
Fintry to Largs. Another interesting group rises througli the Silurian and 
Old Bed Sandstone rocks to the west of the escarpment of the Berwickshire 
plateau, that near Melrose forming one of the largest in Scotland. 
NeikleBm 
Fio. 128. — Section through the large vent of the Campsie Hills. 
1. Andesite lavas ; 2 . Agglomerate and tuft‘ ; 3. Tracliytic and andesitic intrusive rocks. 
Illustrations of tlie varying structure of these vents are given in the 
accompanying figures. In Fig. 1 27, a section is drawn through the two necks 
Misty Law 
J 2 3 3 3 3 2 3 / 3 ^ 43 ^3 3 Z 4- 
Fig, 129. — Biagranimatic section across the central vent of the Clyde plateau in Renfrewshire. 
1. Andesite la\a.s ; 2. Agglomemtes aud fine tails often iimeh altered ; 3. Dykes of tracliytic and andesitic rocks ; 
4. Later dykes of dolerite- and ba.salt. 
Dumgoyn and Dumfoyn, which have already been shown in outline and in 
ground-plan. The relation of these two vents to the neighbouring plateau to 
the right can here he seen. Fig. 128 gives a section taken through the 
