SKETCH OF sEG/NA AND M ETHAN A. 807 



but which, judging from the specimens collected farther east is 

 probably more correctly to be called a dacite. The range of hills 

 (chiefly of late Tertiary marls and conglomerates) in which this 

 rock is found runs east parallel with the north shore of the 

 Saronic Gulf and only a few kilometres distant from it. In these 

 hills is the valley of Sousaki 1 with its mofetti. The rocks of this 

 valley are of serpentine and less altered gabbro, and Reiss and 

 Stiibel are inclined to attribute the emanation of C0 3 and the 

 other phenomena of the mofetti, not to volcanic agencies, but 

 to the decomposition of the gabbro. Philippson combats this 

 view, and I think correctly, though this is not the place to enter 

 into discussion of the matter. Southeast of this, between the 

 range of hills and the sea, is a low hill land, which is mostly 

 " quartz-trachyte " with marl and conglomerate of late Tertiary 

 and Quaternary age. A little to the west of the hamlet of 

 Kolautziki, nine kilometres east of Kalamaki, the railroad cuts 

 through a mass of this dacite, the width of the cut being 112 

 metres. This mass of eruptive rock is in general solid and com- 

 pact, though in places made up of a coarse breccia cemented by 

 finer material of the same nature. No scoriae was to be seen. As 

 Philippson says, it seems to be the end of a lava stream flowing from 

 the west, though he was unable to find its place of origin. This 

 stream is overlaid by late Tertiary limestone, and hence belongs 

 to the same period as the earlier outflows of /Egina. and Methana 



CHARACTER AND DATE OF ERUPTIONS. 



Before passing on to the petrographical description of the 

 various rocks some space must be devoted to the conclusions 

 that may be drawn from the facts observed by myself and others 

 in regard to the character of the eruptions which formed the 

 masses of yEgina and Methana, their geological date, and the 

 order in which the various rocks were poured out. 



In taking up the question of the character of the eruptions 

 we shall start from the most definitely known and least denuded 



J For descriptions of this interesting and little visited locality cf. Philippson, op. 

 cit., p. 22, and the references there given. 



