192 OmOLOGY. 



ring were found near Massowa, as by comparison of 

 them with the species living in the Eed Sea some 

 idea could be formed of the change which has taken 

 place. The beds met with near Massowa must have 

 been, in part at least, of littoral or sub-littoral origin, for 

 the shells which occur in them are evidently marine. 

 Yet if the accumulation took place along the coast, it is 

 strange, unless the character of that coast has altered 

 greatly, that shells and corals are not exceedingly abun- 

 dant instead of being rare. It is very probable that, while 

 some of the sedimentary beds are littoral, others are of 

 sub-aerial origin, and that their materials were washed 

 by streams and floods over the surface of the volcanic 

 beds, like the gravels mentioned in the next section. 



The volcanic series appears to rest on metamorphic 

 rocks, in places at least, both on the Abyssinian and 

 Arabian coasts.^ In both cases, so far as is known, it 

 forms a fringe of varying breadth. 



Hot Springs. — The great prevalence of hot springs along 

 the Abyssinian coast is doubtless connected with the vol- 

 canic formation. Two of the best known of these are that 

 at Ailat, about thirty miles west of Massowa (temp. 150" 

 Fahr.), and that of Atzfut, about eight miles south of ZuUa 

 (temp. 140° Fahr.). The latter is brackish, and probably 

 contains some sea-water, as it issues close by the shore ; 

 the former is excellent, and supplies the vUlage of Ailat. 



1 Although the hills north of Lahej, twenty-five miles from Aden, are 

 volcanic, pebbles of metamorphics are washed down by the streams from 

 beyond in abundance : so it is evident that the rocks crop out a little further 

 inland. 



