Note 18 — Chapter XXIX · THE CARBONIFEROUS VOLCANOES OF ENGLAND

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.

[19] An Enquiry into the Original State and Formation of the Earth, 1778, Appendix, pp. 149, et seq.