chap. in. Ejected Granitic Fragments. 47 



but of a much smaller size, frequently occur at the bases 

 of small cones of eruption. 



Ejected granitic fragments. — In the neighbour- 

 hood of Green Mountain, fragments of extraneous rock 

 are not unfrequently found embedded in the midst of 

 masses of scoriae. Lieut. Evans, to whose kindness I 

 am indebted for much information, gave me several 

 specimens, and I found others myself. They nearly all 

 have a granitic structure, are brittle, harsh to the touch, 

 and apparently of altered colours. First, a white syenite, 

 streaked and mottled with red ; it consists of well 

 crystallised feldspar, numerous grains of quartz, and 

 brilliant, though small, crystals of hornblende. The 

 feldspar and hornblende in this and the succeeding 

 cases have been determined by the reflecting gonio- 

 meter, and the quartz by its action under the blowpipe. 

 The feldspar in these ejected fragments, like the glassy 

 kind in the trachyte, is from its cleavage a potash- 

 feldspar. Secondly, a brick-red mass of feldspar, quartz, 

 and small dark patches of a decayed mineral ; one 

 minute particle of which I was able to ascertain, by its 

 cleavage, to be hornblende. Thirdly, a mass of con- 

 fusedly crystallised white feldspar, with little nests of a 

 dark coloured mineral, often carious, externally rounded, 

 having a glossy fracture, but no distinct cleavage : from 

 comparison with the second specimen, 1 have no doubt 

 that it is fused hornblende. Fourthly, . a rock, which 

 at first appears a simple aggregation of distinct and 

 large-sized crystals of dusky-coloured Labrador feldspar j 1 



1 Professor Miller has been so kind as to examine this mineral. 

 He obtained two good cleavages of 86° 30' and 86° 50'. The mean 

 of several, which I made, was 86° 30'. Prof. Miller states that these 

 crystals, when reduced to a fine powder, are soluble in hydrochloric 

 acid, leaving some undissolved silex behind ; the addition of oxalate 

 of ammonia gives a copious precipitate of lime. He further re- 

 marks, that according to Yon Kobell, anorthite (a mineral occurring 

 in the ejected fragments at Mount Somna) is always white and 



