Note 7 — Chapter XXIX · THE CARBONIFEROUS VOLCANOES OF ENGLAND

"Whin" is a common term in Scotland and the North of England for any hard kind of stone, especially such as can be used for making and mending roads. "Sill" denotes a flat course or bed of stone, and was evidently applied to this intrusive sheet from its persistent flat-bedded position and its prominence among the other gently inclined strata among which it lies. It is from this example in the North of England that the word "sill" has passed into geological literature.

[8] On the coast at Bamborough and the Harkess Rocks the usual petrographical characters of the Whin Sill are exchanged for those of fine-grained amygdaloidal diabases arranged in distinct sheets, which in their upper parts are highly vesicular and show ropy surfaces—peculiarities suggestive of true lava-streams. But according to Professor Lebour the rocks are intrusive into limestone and shale (Geology of Northumberland and Durham, p. 98). Mr. Teall has expressed the suspicion that these rocks must have consolidated under conditions somewhat different from those which characterized the normal Whin Sill (Quart. Journ. Geol. Soc. xl. p. 643). They seem to be the only parts of the sill which present features that might possibly indicate superficial outflow.