168 GEOLOGY. 



neighbourhood of Ain and Af Abed, in Habab (lat. 15° 55' 

 to 16° ]0' N.), as far south as the metamorphic rocks 

 were found to predominate on the highlands, and that is 

 to about twenty-five miles south of Adigrat (or nearly 

 13° 50' N.), or throughout a distance of upwards of 150 

 miles from north to south. In the Anseba valley, and 

 around Keren, in Bogos, the strike changes to north-east 

 and south-west; and very possibly this direction may 

 prevail to the northward. 



To the constancy of the strike of the metamorphic 

 rocks several of the most important features are due, one 

 of the principal being the direction of the river valleys. 

 No one can have studied the geographical sketches made 

 during the progress of the expedition, of the physical 

 features of the country around the passes, without ob- 

 serving the remarkable manner in which the principal 

 valleys, such as those of Komayli and the Haddas, run 

 for many miles in a north and south direction, parallel 

 to the base of the hills, before debouching into the plain. 

 As the facility with which an excellent military road 

 was made to the highlands was due mainly to the length, 

 and consequently gentle slope, of the ravines traversed, it 

 is very evident that the accessibility of Abyssinia from 

 the sea depends, in a great measure, upon the geological 

 structure of the rocks, and that the foliation of the gneiss 

 was one of the best friends of the British army during its 

 ascent to the highlands. 



Keference was made on the previous page to an in- 

 stance being met with, at the base of one of the hills near 

 Senafe, of the original bedding being still perceptible in 



