Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/423

 red bole or earth not unfrequently occur. I have noticed similar partings between old lavas at Torre del Annunziata; and in the latter case, at least, they can hardly be regarded as other than the soil which had gathered over the older lava, and was burnt by the overflow of the newer one.

The following tabular arrangement will show at a glance the classification of the rocks which I have adopted : —

Classification of the Tertiary Igneous Rocks of Britain.

Felspathic Series.

Pyroxenic or Augitic Series.

A. Crystalline Sheets or beds.

B. Fragmental. Beds or layers In this Table are inserted only those rocks which I have myself, up to this date, found among the Tertiary series. The list will, no doubt, be enlarged as further investigations proceed f.

3. Geological Age of the Rocks.

A few words are needed here in support of the view that all the rocks now to be described are of Tertiary age. In Antrim the well- known position of the basalt above the chalk, and its association with layers containing miocene plants — in Mull the occurrence of a thick bed of chalk-flints, and of the Ardtun miocene leaf-beds i, at the base of the whole volcanic series, the evident prolongation of the Mull volcanic rocks through the other islands of the Inner Hebrides §, f I have given a more detailed account of this classification of volcanic rocks, and of the grounds on which it is based, in Chapter xiii. of the forthcoming edition of Jukes' s ' Manual of Geology.'

% See Quart. Journ. Geol. Soc. vol.vii. p. 90.

§ Following Edward Forbes, I formerly regarded the volcanic rocks of Skye as of Oolitic age, being misled by the way in which the basalts at their base seem