WESTER LOMOND. 133 



On crossing the trap ridge of Wester Lomond, horizon- 

 tal strata of mountain limestone are found resting upon it. 

 Quarrying operations have not as yet exposed the green- 

 stone on which this limestone reposes, but its aspect through- 

 out its whole visible extent is a sufficient proof that it has been 

 influenced in no inconsiderable degree by the agency of the 

 trap. The smooth conchoidal fracture, the earthy appear- 

 ance, and uncrystalline arrangement, of the mountain lime- 

 stone have all been removed, and a rock produced which 

 in many places, is perfectly crystalline in its structure, and 

 of various shades of grey and white. The usual corals and 

 madrepores occur in this limestone, and, in their states of 

 preservation, vary from one, which in the rock when little 

 altered, is almost perfect, to that more or less obliterated 

 appearance which they present when found in the complete- 

 ly altered limestone. 



The trap forming the range of Wester Lomond, is a 

 greenstone which varies from large to small granular ; it is 

 in general arranged in concretions having a tendency to the 

 prismatic form ; but, in some places, it displays, in the most 

 marked manner, the globular appearance. Mid-Lomond, 

 as we have before stated, is, in its lower part, composed of 

 sandstone strata, and in the upper of trap. Induration is, 

 however, in no instance to be observed. On the side of the 

 valley which separates this hill from Wester Lomond the 

 trap may be found alternating several times with the sand- 

 stone ; the state of the surface, however, prevents us from 

 examining the appearances exhibited at the junction of the 

 two classes of rock. The trap-rock which forms the lower 

 parts of Mid-Lomond, is an ordinary greenstone with some- 

 what of a prismatic structure ; the summit, however, and 

 a considerable part of the southern acclivity, is entirely 

 composed of a well characterized greyish-black basalt, which 



