the Western Part of Asia Minor. 29 



\st period. — A mass of basalt of the first period caps the platform of lacustrine 

 limestone on the north side of the Hermus for a distance of several miles, and may 

 be seen in the distance in the sketch (PL III. fig. 11). The greater part of it sphts 

 into irregularly wedge-shaped masses ; but in a hollow on the south side, there is 

 a fine section of columnar basalt, divided into two beds. In the lower, the columns 

 are uniformly perpendicular ; but in the upper bed they diverge to each side with 

 a shght curve, as seen in the accompanying wood-cut in the preceding page. 



This vast tabular mass of basalt is here above 100 feet thick, but in general it 

 does not much exceed 50 feet. A bed of soft sand intervenes in some places be- 

 tween the limestone and the basalt, but the junction-beds are in general obscured 

 by a talus of basaltic fragments. 



The summit of this basaltic plateau is about 800 feet above the bed of the Her- 

 mus, proving the vast amount of denudation which has taken place since the pe- 

 riod of its eruption. The source from which the basalt has flowed is no longer 

 apparent. 



On the S.W. of this plateau, and on the opposite side of the Hermus, is a small 

 insulated hill of horizontal limestone, also capped by basalt at the same level. Its 

 base is encircled by streams of lava of the 2nd and 3rd periods, which have flowed 

 since the excavation of the valleys. The limestone at the base of the hill has un- 

 dergone alteration, and is converted into a yellow jasperine substance with a bright, 

 conchoidal fracture (PI. II.). 



About five miles east by south from Koola, close to the foot of the schistose 

 hills which skirt the lacustrine basin, is a small plateau of imperfectly columnar 

 basalt, which is referable to the 1st period. It is seen in the foreground of the 

 sketch (PI. III. fig. 11). The lacustrine beds on which the basalt reposes, being 

 near their junction with the older rocks, consist, in this place, of gravel and sand, 

 derived from the schistose formation (PL II. and PL III., Sect. 8). 



On the south side of the Hermus, about five miles N.N.W. from Koola, is an- 

 other large insulated plateau of basalt, reposing on the lacustrine formation (PL II.). 



Ind period. — To the second period of volcanic action, we refer the numerous 

 conical hills of scoriae and ashes, which cover the schistose ridges on the south of 

 the lacustrine formation. The range of mica-schist and marble, which runs from 

 east to west on the south of Koola*, sends off three nearly parallel ridges towards 

 the north, and may therefore be compared to the letter E. (PL II.) The volcanic 

 cones of the second period are scattered along this principal ridge and its three 

 lateral branches, and many streams of lava may be traced flowing from them, 



* These schistose hills form part of the northern base of the Tmolus range. 



