IO 
THE CARBONIFEROUS VOLCANOES 
BOOK VI 
Though the “ toadstones ” were believed to form definite platforms 
among the limestone strata, and thus to be capable of being used as 
reliable horizons in the mineral fields of Derbyshire, they appear to 
have been generally regarded as intrusive sheets like the Whin Sill of 
the north. Thus De la Beche in his Manual of Geology, giving a 
summary of what was known at the time regarding intercalated igneous 
rocks, remarks with regard to the Derbyshire toadstones that they may 
from all analogy be considered to have been injected among the limestones 
which would be easily separated by the force of the intruded igneous 
material. 1 But the same observer, after his experience among the ancient 
volcanic rocks of Devonshire, came fully to recognize the proofs of contem- 
poraneous outflow among the Derbyshire toadstones. In his subsequently 
published Geological Observer, he described the toadstones as submarine 
lavas that had been poured out over the floor of the sea in which the 
Carboniferous Limestone was deposited, and had been afterwards covered up 
under fresh deposits of limestone. 1 It is remarkable, however, that he 
specially comments on the absence, as he believed, of any contemporaneously 
ejected ashes and lapilli, such as occur in Devonshire. That true tuffs or 
volcanic ashes are associated with the toadstones was noticed by Jukes 
in 18 61, 3 and afterwards by the Geological Survey. 4 Since that time 
geologists have generally recognized these Derbyshire igneous rocks as truly 
contemporaneous intercalations. But very little has recently been written 
on the structure of the district, our information regarding it being still 
based mainly on the early observations of Fairey and the mapping of the 
Geological Survey. 
The subject, however, has now been resumed by Mr. H. Arnold Bemrose, 
who m 1894, after a prolonged study of the petrography of the rocks’ 
communicated the results of his researches to the Geological Society. 5 In 
his excellent paper, to which I shall immediately make fuller reference, he 
mentions the localities at which lava-form and fragmental rocks may be 
observed, but does not enter on the discussion of the geological structure of 
the region or of the history of the volcanic eruptions. Before the announce- 
ment of his paper, hearing that I proposed to make for the first time a rapid 
traverse of the toadstone district, for the purpose of acquainting myself with 
the rocks on the ground, he kindly offered to conduct me over it. My chief 
object, besides that of seeing the general nature of the volcanic phenomena 
of the region, was to examine more particularly the areas of the volcanic 
fragmental rocks, with the view of discovering whether among them some 
lemams might not be found of the actual vents of discharge. In this search 
1 was entirely successful. Aided by Mr. Bemrose’s intimate knowledge of 
3 Z M edl ^' ! 833 ’ p - 462 - 2 Geological Observer (1851), pp. 642-645. 
Student s Manual qf Geology, 2nd edit. (1863), p. 523. For a general’ rtsuvi 4 of the proofs of 
A hXT^ riu 1 n! e toadstones ’ see “ Tho Geol °gy of North Derbyshire,” by Messrs. 
A. i . Green and A. Strahan (Memoirs of the Geological Survey, 2nd edit. (1887), p. 123). 
In the first edition of the Memoir on the Geology of North Derbyshire, published in 1859, the 
authors of which were Messrs. A. H. Green, C. le Neve Foster and J. R. Dakyns 
Quart. Journ. Geol. Soc. vol. 1. (1894), p. 603. 
