6 MALLET : ADEN AND VICINITY, 



to dip radially from h and not from c, and in the spurs south-east of the 

 Gold-mohur valley, which run vsrest-south-west from Shumshum, the strata 

 dip roughly speaking from h and at right angles to a radius drawn 

 from c ; time did not permit me to work out this point satisfactorily, but 

 it is one worth investigation. Supposing there to be a second crater, the 

 more imperfect state of h, the greater extent to which it has suffered 

 from the wasting influence of rain and sea would xjrimd facie tend to 

 indicate a greater age for it than for c, for we cannot well suppose both 

 to have been in action at the same time, although eruptions may have 

 taken place to some extent alternately, sometimes from one, sometimes 

 from the other, that is to say, one may have been still active at the time 

 of the breaking out of the second. The Twin rock and the Feringhee 

 islets in the harbour may be remnants of the crater h, and Swayeea 

 islet a spur from it, like Marshag from the cantonment crater. 



The varieties of rock met with are very numerous ; there are 

 perfectly compact lavas of brown, grey, and dark green tints, sometimes 

 containing crystals of augite and not unfrequently those of sanidin, and 

 there are rocks exhibiting every degree of vesicularity until we arrive 

 at lavas resembling a coarse sponge and passing into scoriae. The 

 vesicles again are in some specimens globular, and in others flat and 

 drawn out. In some places the lava is quite schistose, and might if seen 

 per se be easily mistaken for a metamorphic rock. Such lava is some- 

 times vesicular but by no means always so, at least not to the naked 

 eye. Volcanic breccias are also met with, as near the main pass where 

 fragments of dark green lava are imbedded in a reddish matrix. Tufas 

 are also present but apparently to a limited extent. Some specimens 

 of Tufa shown to me by Captain Mander, the Executive Engineer, were 

 made up principally of fragments of pumice, from which it would 

 appear that pumice must be amongst the volcanic products, though I am 

 not aware of any locality in which it is found in situ. Obsidian is to be 

 met with occasionally in thin seams. 

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