284 GENERAL COMPARISON OF 



that occurs, being the single set of strata that forms the 

 grey ridge of Seil and Luing so often mentioned and alter- 

 nates with the clay slate of this tract. The southern limit 

 however is unassignable; a great number of indefinite 

 gradations and irregular alternations taking place, before 

 the chlorite series is finally established to the exclusion of 

 the micaceous schist which forms the southern part of 

 Cantyre and the districts to the south of Loch Fine. This 

 ambiguous tract however rarely exceeds two miles in 

 breadth ; in a few places it may extend to four. 



Many opportunities of tracing these alternations are 

 afforded, in the sections presented by the various shores 

 of these intersected coasts. The micaceous schist pos- 

 sesses a very uniform character through the whole extent 

 above mentioned ; being generally of a greenish hue, so as 

 slightly to approach to chlorite schist, without ever pre- 

 senting very decided examples of it. Occasionally also it 

 assumes a quartzose character, without actually passing 

 into quartz rock. It appears to contain no beds of any 

 substance, excepting some partial tind irregular masses 

 of limestone. In general it is much undulated, and in 

 this respect it offers a marked contrast to the chlorite 

 series, which is characterized by the great straightness 

 and even parallelism of the beds. 



The gradation between the micaceous schist and the 

 chlorite series takes place by the occasional occurrence 

 of one or other of the beds of the latter among those 

 of the former. At first, a single one only will be found 

 in a space of many hundred yards, but at length in- 

 creasing in frequency, they become predominant; the 

 micaceous schist gradually diminishing in such a manner 

 as to be no longer perceptible except on close examination. 

 During the progress of this change, the stratification, 

 which, through nearly the whole extent of the micaceous 

 schist, is so confused as to be scarcely distinguishable, 

 becomes gradually so even and regular, that, in those 

 cases where the angles of inclination are small, the 



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