SKETCH OF JEGINA AND M ETHAN A. 8l I 



of strato-volcanoes, built up of explosive ejection of fragmentary 

 material and the pouring out of liquid lava streams, of which 

 Vesuvius and Etna are taken as types. Tuff exists, it is true, in 

 some places on /Egina, as we have seen, but here it exists on the 

 surface, overlying the massive rock at the flanks of the moun- 

 tain, and it is well known that such deposits do accompany vol- 

 canic domes. Lava sheets are, however, quite lacking. It is 

 evident from an examination of the region that the denudation 

 has not been very extensive, so that the absence of tuff cannot be 

 explained on this ground ; any amount of which, moreover, would 

 not explain the absence of inter-stratified tuff beds and lava 

 sheets. The denudation has not been nearly as extensive as that 

 which has taken place in the somewhat similarly formed 

 Euganean Hills near Padua in Northern Italy, where the erup- 

 tions ceased in post-Eocene time, 1 though it must be remarked 

 that the climate is here more favorable to denudation than in 

 our region. The main valleys between the mountain masses 

 must hence be looked on as original intercolline spaces, enlarged, 

 though slightly, by erosion. 



The forms of the mountain masses and their mutual positions 

 are decidedly those to be looked for in the case of eruptions of 

 the kind supposed, and different from those produced by the 

 erosion of a strato-volcano. While not of the regular "bell" 

 shape that is seen in such perfection in the "fiuys" of the 

 Auvergnes or the "mamelons" of Reunion, yet the shape of the 

 ridges is eminently such as would be produced by the extension 

 of a mass of viscid lava (without the formation of explosion 

 craters) at many points along a fissure, such as have been 

 described by Scrope 2 and Hartung. 3 The masses are higher and 

 shorter than those which would be formed by liquid lava streams, 

 and they do not, except in the case of Mt. Oros, radiate from a 

 common centre. 



The character of the lavas also is eminently favorable to the 



j Reyer, Die Enganeen, Wien, 1877, p. 48. 



2 Scrope, Volcanoes, 2nded., 1862, p. 134. 



3 Hartung, Beobacht. iiber Erhebungskrater, etc., Leipzig, 1872, p. 57. 



