[19] An Enquiry into the Original State and Formation of the Earth, 1778, Appendix, pp. 149, et seq.
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.[20] The first detailed account of the Derbyshire eruptive rocks was that given by Fairey,[21] 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.[22] 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.[23]
[20] Trans. Roy. Soc. Edin. i. p. 275, et seq. Hutton specially mentions the toadstone of Derbyshire as one of the rocks produced by fusion, p. 277.
[21] General View of the Agriculture and Minerals of Derbyshire (1811).
[22] Outlines of the Geology of England and Wales (1822), p. 448.
[23] 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.
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.[24] But the same observer, after his experience among the ancient volcanic rocks of Devonshire, came fully to recognize the proofs of contemporaneous 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.[25] 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 1861,[26] and afterwards by the Geological Survey.[27] 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.
[24] Manual, 3rd edit. 1833, p. 462.
[25] Geological Observer (1851), pp. 642-645.
[26] Student's Manual of Geology, 2nd edit. (1863), p. 523. For a general résumé of the proofs of contemporaneity furnished by the toadstones, see "The Geology of North Derbyshire," by Messrs. A. H. Green and A. Strahan (Memoirs of the Geological Survey, 2nd edit. (1887), p. 123).