248 ISLA. GEOLOGY. 



is obvious that they are placed in parallel alternating 

 order with these. 



A smaller tract of the same limestone is found near 

 the Duich river. In some places the alluvial soil prevents 

 this from being traced to the former more extensive mass ; 

 while, in others, it is obvious that the quartz rock inter- 

 venes so as in some measure to prevent the one from 

 being prolonged, according to the bearings of the strata, 

 to the other. It must probably be considered as a distinct 

 portion, occupying a series of beds forming a double 

 wedge ; since it cannot be traced to the southward, where, 

 if it existed, it must appear on the sea shore. Similar 

 masses are so common where limestone occurs among 

 the primary strata, that the present instance can excite 

 no surprise. 



The last portion of this limestone occurring in Isla 

 is found on the shore about a mile to the westward of 

 Ardmore point. This is in a vertical position, and al- 

 ternates with very thin beds of clay slate, like the two 

 former. The prolongation of the strata does not permit 

 it to be considered as part of the mass last mentioned ; 

 and it must therefore be supposed a similarly independent 

 portion. 



The next limestone is in very small quantity, and bears 

 the same relation to micaceous schist, as that last de- 

 scribed does to clay slate. The same description, with 

 the requisite alterations, will therefore serve for both, 

 except that the colour of this is grey or whitish. The 

 geological connexions are as obscure as those of the forme^ 

 and I may add, that I only observed it in the neighbour- 

 hood of Portaskeg. 



- The third is of a different character, and although it 

 does not appear to occupy a great extent, its connexions 

 are to a certain degree apparent and its history com- 

 paratively satisfactory. It is most easily seen in Lossit 

 hill, forming beds of considerable thickness, and alterna- 

 ting with the quartz rock; the ordinary inclination of 



