TRAPPEAN SERIES. 187 



nothing to indicate the geological age of this very in- 

 teresting group of traps. No other formation was seen 

 resting upon it ; it caps all the highest hills observed, 



It is highly probable that the trap rocks of Shoa 

 belong, in part at least, to this group. No idea can be 

 formed of their extension further south, nor is it possible 

 to say whether the trappean formations which cover so 

 large an area in Central Abyssinia should be referred to 

 the Magdala or the Ashangi group. In aU probability 

 both are represented. There can be but little doubt, 

 however, that the traps on the hills west of Adigrat 

 belong to the higher group. Although the lower beds 

 consist of basalt alone — and from want of time it was 

 impossible to examine the higher hills — the cliff-like 

 scarps are just as conspicuous amongst them as farther 

 south ; and these appeared, wherever they could be 

 examined, to be characteristic of the trachytes. The 

 conformity to the Adigrat sandstone is in all probability 

 only apparent. 



The volcanic rocks of the neighbourhood of Senafe 

 differ from those of Adigrat and. the south in the absence 

 of any marked bedding, and to some extent also in 

 mineral character. They consist chiefly of trachyte, 

 but this is frequently so jfine-grained and compact, that 

 even with the aid of a lens it is very difficult to dis- 

 tinguish it from a sedimentary rock, being in fact what 

 is generally termed claystone. The crags just west of 

 the camp at Senafd were most naturally mistaken by 

 everybody in the army for sandstone.^ These hills are 



' As already mentioned, it was some time before I was myself undeceived 



