1871.] 



GEIKIE TERTIARY VOLCANIC ROCKS. 



283 



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 Bocks 



Of 



Britain. 







Pelspathio Series. 



Pyroxenic or 

 Augitic Series. 



1 



§ 



O 1) 



Ph 



•a 



11 



ta o 



PI 



1 



I 



1 



1 





i 



O 



I. Interbedded ok Contempora- 

 neous. 

 A. Crystalline. 



Sheets or beds , . . 







? 



? 



V 



* 

 * 



* 



* 



? 



* 

 ? 



* 



* 



? 



* 



B. Fragmented. 







II. Intrusive or Subsequent. 

 A. Crystalline. 



a. Amorphous masses 



/3. Sheets 



* 



* 



y. Dykes and veins 



S Necks 



* 



¥: 

 ? 



B. Fragmental. 



Necks 











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 BocTcs. 



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 J, 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 



