D J. MILNE ON THE SINAITIC PENINSULA AND N.W. ARABIA. 



On the right or south side is a granite, whilst on the left or north 

 side there are beds of sandstone and conglomerate. 



The granite, which is more or less of a reddish colour, is in such a 

 decomposed state on its surface, that at a short distance it would be 

 readily mistaken for a soft sandstone. Even in the more solid parts, 

 when struck with a hammer it readily falls into angular pieces. Its 

 texture varies considerably, being both fine and coarse ; but in all 

 parts the felspathic element predominates. The striking feature in 

 this rock is the number of dykes by which it is traversed. These, 

 generally speaking, have a strike from north to south, and a dip at 

 a high angle of 80 or 85° towards the east. 



In all the granite hills of these regions, there are visibly two 

 classes of dykes, which are distinguishable from each other by their 

 colour — black ones, which are generally dark-coloured coarse- 

 grained porphyries, and red ones, which are for the most part pink 

 felsites or fine-grained porphyries. Both of these are much disinte- 

 grated, but the former more so than the latter. On an east and west 

 section about a quarter of a mile in length, out of eleven of the 

 dark-coloured dykes, only two stood up to form peaks ; the remaining 

 nine, being softer than the granite, were cut down so as to form 

 hollows and heaps of debris. 



About half a mile up this valley, upon its south side, a bluff 

 about 30 feet in height rises perpendicularly from the top of a large 

 mound. This appears to show a junction of the granite and con- 

 glomerate ; but the two externally appear to be so merged into each 

 other that it is difficult to draw a marked line between them. The 

 top of the bluff is covered with two horizontal bands of sand and 

 rounded stones about six feet in thickness. On its southern side, 

 beneath this cap there is a face of decomposing felspathic granite, 

 traversed by greenish-coloured dykes, which include within them- 

 selves small angular fragments probably derived from some earlier- 

 formed dyke which they have traversed. Passing round to the 

 east side, there is an apparent gradation into red earthy bands, 

 very like a hard clay, which in their turn merge on the north side 

 into a brecciated conglomerate, which faces the sandstone beds 

 on the opposite side of the valley. This conglomerate varies 

 considerably in texture, containing not only pebbles, but also large 

 boulders. Facing this bluff, upon the opposite side of the valley, 

 which is here considerably narrowed, there is a corresponding bluff 

 formed wholly of conglomerate. The upper part of this, which is 

 made up of a coarse material, the stones it contains being as 

 large as a cocoa-nut, lies unconformably upon a bed of finer 

 material. 



This lower bed in its upper portions is a gritty sandstone, but as 

 it descends it passes into a fine conglomerate. Being much softer 

 than the rock which caps it, it is rapidly being undermined, and 

 large blocks of the coarse conglomerate from above are in conse- 

 quence continually falling. These blocks, although they are made 

 up of similar, if not the same, material as the neighbouring granite 

 rocks, form, as far as their durability is concerned, a far superior 



