Vol. 56.] THE SOUTH-EASTERN COAST OF JERSEY. 313 



hornblendes, and is finally seen to cut and break up the darker older 

 rock as above described (p. 312). The whole passage from coarse to 

 quite fine takes place well within 6 yards, but the very coarse variety 

 appears in patches and clot-like streaks. In one place a shadowy 

 band can be traced on the weathered surface of the rock for 11 or 

 12 yards, composed of ill-defined patches, which represent fragments 

 in more or less complete stages of dissolution. This rock, 

 variable in composition and non-homogeneous in origin, passes 

 into a rather finely-mottled black-and-white rock with numerous 

 large hornblendes irregularly spread through it. In some places 

 the passage is fairly regular and gradual, at others more sharply 

 defined. Specimens may be found, in which the coarse intergrowth 

 of hornblende and felspar forms bands separated the one from the 

 other by much more finely-mottled material ; others contain in- 

 definite patches of the same kind. 



This finely-mottled rock differs from the coarse rock with the 

 elongated hornblendes in one or two important points. In the 

 former the hornblende either is a matrix for the earlier consolidated 

 felspar, or occurs in grains seldom if ever idiomorphic. Paler and 

 fibrous patches suggest original augite. There is little to distinguish 

 these sections from those of a diabase. Although a few grains of 

 quartz are found, and also a little orthoclase as usual wedged in 

 between the other constituents, the conclusion is suggested that 

 these are fragments of the diabase which have escaped dissolution. 

 The traces of acid minerals might be expected, when the changes> 

 which the surrounding rock has undergone are considered. 



(4) The Granite or Later Acid Intrusion. 



The granite of the Eastern District forms the more outlying crags 

 of Greve d'Azette and St. Clement's Bay. It is a pinkish or pale 

 flesh-coloured rock of medium grain, containing orthoclases nearly 

 \ inch long, and occasionally twice that size. Quartz is present 

 in some quantity ; hornblende and mica are decidedly scarce. A thin 

 section shows the dominant constituent to be orthoclase, slightly 

 kaolinized and exhibiting the usual inicroperthitic intergrowth ; 

 quartz, in groups of grains without a granophyric relation to the 

 felspar ; and a little albite, or an altered plagioclase. There are a 

 few small flakes of a brownish-green, rather fibrous mica. The rock 

 shows a close resemblance to the earlier porphyritic intrusion of 

 Sorel Point; its specific gravity, as determined by a Walker's 

 balance, is the same : namely, 2-60(3. 



The incorporation of diabase-fragments by this granite is quite 

 local, and it is often far from easy to decide whether any one 

 instance is due to the intrusion of this rock or to that which 

 produced the earlier brecciation described on p. 308. With the aid of 

 the microscope, however, much of this difficulty disappears, thanks 

 in great measure to resemblances shown to the rocks of Sorel Point. 

 Here, as there, we have unequivocal evidence of change amounting. 



