CHAP. XXIX 
THE DERBYSHIRE TOADSTONES 
19 
Great Rocks Quarry, Peak Forest 
in other examples, a remarkably 
® a y sometimes be observed, as at the 
homeworks (Fig. 181). In this, as 
ummocky and uneven surface of lime- 
stone lies below the igneous band, 
t e calcareous rock presenting knobs 
and ridges, separated by cauldron- 
8 a P e d cavities and clefts, some of 
which are several yards deep. These 
inequalities are filled in and covered 
over with a soft yellow and. brown 
? a 7> varying up to three or four feet 
thickness, and passing upwards into 
tie more solid toadstone. There can 
aidly be any doubt that this singu- 
arl T uneven limestone surface is due 
to the solvent action of water lying 
etween the limestone and the some- 
vliat impervious toadstone above, and 
at the clay represents partly the 
insoluble residue of the calcareous rock, but chiefly the result of the action 
°f the infiltrating water on the bottom of the igneous band. 1 
Junctions of the upper surfaces of the lava-sheets with the overlying 
limestone show that the igneous material sometimes assumed hummocky 
forms, which the calcareous deposits gradually overspread and covered. A 
,-mod example of this kind may be observed by the roadside at the foot ot 
haven’s Tor, Millersdale. As shown in the subjoined figure, the limestone 
Fig. 181. — Section of vesicular and amygdaloidal 
diabase resting on Carboniferous limestone, 
Peak Forest Limeworks, Great Rocks Quarry. 
1. Limestone with a surface dissolved into cauldron-like 
hollows ; 2. Rotten yellow and brown clay resulting 
from decomposition of toadstone and white clay 
from the solution of the limestone— sometimes three 
or four feet thick ; 3. Toadstone, a diabase with 
highly slaggy base. 
182. — View of the superposition of Carboniferous limestone upon toadstone, Raven’s Tor, 
Millersdale (length about 100 feet). 
1. Toadstone; 2. Limestone;/, Fault. 
kas here been worn into a cave, the floor of which is formed by the toad- 
stone. The latter rock, of the usual dull green, slaggy and amygdaloidal 
character, is covered immediately by the limestone, but I did not observe 
aa y fragments of the toadstone, nor any trace of ashy materials in the over- 
lying calcareous strata. This section shows that after the outflow ol .the 
lava > the sedimentation of the limestone was quietly resumed, and the igneous 
interruption was entirely buried. 
1 Geological Survey Memoir on North Derbyshire , p. 20 and. footnote. 
Compare De la Beche, Geological Observer , pp. 559, 560, and North Derbyshire Memoir, p. 128. 
