CHAP. XXIX 
THE DERBYSHIRE TOADSTONES 
9 
from Yorkshire to the Midland plain, and separates the eastern from the 
western coal-fields. This fold widens southwards until not only the Millstone 
Grit and Yoredale rocks, but the underlying Mountain Limestone is laid hare. 
A broad limestone district is thus exposed in the very heart of the country, 
ranging as a green fertile undulating tableland, deeply cut by winding 
valleys, which expose admirable sections of the strata, but nowhere reach 
the base of the system. The total visible depth of the limestone series is 
computed to be about 1500 feet; the Yoredale shales and limestones may 
be 500 feet more ; so that the calcareous formations in which the volcanic 
phenomena are exhibited reach a thickness of at least 2000 feet. 
It is not yet definitely known through what vertical extent of this 
thickness of sedimentary material the volcanic platforms extend, but where 
most fully developed they perhaps range through 1000 feet, lying chiefly in 
the Carboniferous Limestone, but apparently in at least one locality extending 
up into the lower division of the Yoredale group. The area within which 
they can be studied corresponds nearly with that in which the limestone 
forms the surface of the country, or a district measuring about 20 miles 
from north to south, with an extreme breadth of 10 miles in an east and 
west direction. 
A special historical interest belongs to the Derbyshire " toadstones.” 1 
They furnished Whitehurst with material for his speculations, and were 
believed by him to be as truly igneous rocks as the lava which flows from 
Hecla, Vesuvius or Etna. But he thought that they had been introduced 
among the strata and “ did not overflow the surface of the earth, according 
to the usual operations of volcanoes.” 2 
His views were published as far back as 1778, three years after 
Hutton read the first outline of his theory of the earth and made known 
his observations regarding the igneous origin of whinstones. 3 The first 
detailed account of the Derbyshire eruptive rocks was that given by 
Fairey, 4 which has served as the basis of all subsequent descriptions. 
Conybeare, in particular, prepared a succinct narrative from Fairey’s 
more diffuse statements, and thus placed clearly before geologists the 
nature and distribution of these volcanic intercalations. 5 Subsequently 
the district was mapped by De la Beche and the officers of the 
Geological Survey, and the areas occupied by the several outcrops of 
igneous rock could then be readily seen. 0 
1 This word has by some writers been supposed to be corrupted from tod-stein, dead-stone, in 
allusion to the dying out of the lead veins there ; by others the name has been thought to 
be derived from the peculiar green speckled aspect of much of the rock, resembling the back 
of a toad. 
2 An Enquiry into the Original State and Formation of the Earth, 1778, Appendix, 
pp. 149, at seq. 
3 Trans. Roy. Soc. Ediu. i. p. 275, et seq. Hutton specially mentions the toadstone of Derby- 
shire as one of the rocks produced by fusion, p. 277. 
4 General View of the Agriculture and Minerals of Derbyshire (1811). 
5 Outlines of the Geology of England and Wales (1822), p. 448. 
0 See Sheets 71 N.W., 72 N.E., 81 N. E. and S.E. and 82 S.W. of the Geological Survey of 
England and Wales. 
