THE TRAP ISLANDS. 71 



this island a conglomerate and a sandstone, of a red and 

 of a grey colour, lie immediately on the primary strata. 

 There can be no doubt of the analogy of these rocks 

 to the ordinary red sandstone which, in the central parts 

 of Scotland, immediately follows the primary strata ; and 

 it is apparent that they are here succeeded in immediate 

 superposition by the white calcareous sandstone. The 

 general conclusions respecting this scattered series will 

 not however be affected, even if the place of the limestone 

 on the western side of Mull and on Inch Kenneth be 

 conceived to lie above the calcareous sandstone, as, in 

 other situations, these substances are known to alternate. 



The following general conclusion may be drawn from 

 these facts. The gneiss of Mull and Morven are portions 

 of the same mass of strata, and have originally been 

 covered by a deposit of secondary rocks, consisting of 

 limestone and sandstone with coal occasionally inter- 

 spersed. The essential characters of this deposit corre- 

 spond with those of the northern islands, and no less 

 with the more extensive tracts which occupy the centre 

 of Scotland; of which a portion, similarly detached, and 

 strongly corresponding in position and present connexions 

 with this, is still to be found near the Mull of Cantyre, form- 

 ing the present coal field of Campbelltown. This tract of 

 secondary strata has, both in Mull and in Morven, been 

 overwhelmed by a deposit of trap, of which disjoined 

 portions only, of greater or less magnitude, are still 

 existing. To this rock, and to the consequences of its 

 subsequent partial destruction, is now owing the obscurity 

 which attends these strata ; and from its interference in 

 various modes, has in a great measure arisen the present 

 scattered state of their fragments. This case is so parallel 

 to that of Sky, that it requires no further comment; 

 although presenting some very interesting points of dif- 

 ference. 



It is now necessary to investigate the connexion between 

 the strata of Mull and those that are found in the northern 



