796 THE JOURNAL OF GEOLOGY. 



forms the neighboring mountains, and seem to represent in part 

 an ancient talus, worn by the action of the sea and subsequently 

 cemented by the travertine-like material which partially forms 

 the shore deposits. This sort of breccia is to be found up to 

 heights of 200 metres. 1 



The most northerly mass of eruptive rock is that of the 

 Stavro District, including the domes of Mts. Stavro (311 m.), Palae- 

 ochora, and Spasmeno Vouno, and much of the lowest slopes 

 of these is formed of the breccia just described. Mt. Stavro 

 (Cross Mt.), which is formed of a compact mass of hornblende- 

 andesite, presents some interesting peculiarities of structure. As 

 we pass along the west side of the valley, between it and Palaeo- 

 chora we see that its east face, which is very steep above but 

 more sloping below, is cut here and there by vertical joints run- 

 ning east and west. In one place two of these parallel joints are 

 only four metres apart, and the intervening mass has slipped 

 down some two metres, giving rise to slickensides on the two 

 faces of the adjoining rock. The side walls show a columnar 

 structure perpendicular to the vertical face. This columnar 

 structure is very well developed around the whole east and north 

 sides of Mt. Stavro, the irregular columns varying from 1 5 to 

 50 cm. in diameter, and on the northeast side dipping towards 

 the southwest. They are cut by many transverse, but not decid- 

 edly "ball and socket" joints, one effect being that the east slope 

 of the mountain is quite free from debris, while the north and 

 northeast sides have their lower slopes thickly covered with a 

 talus of angular fragments broken off from the columns above. 

 The columns are often curved, and in some places a sub-spherical 

 structure is developed. The upper part of the north face of 

 the mountain is quite vertical, and shows a peculiar structure 

 which, as it seems rather out of the ordinary, may be briefly 

 described. Two straight vertical joints, running north and south, 

 cut the rock face, and on each side of both of these is a second- 

 ary system of curved joints which meet the vertical joints at 

 angles of 45 ° to 6o°, curving downwards and approaching a ver- 



I B. & v., 258, R. & s., 15. 



