MULL. GEOLOGY. 575 



as they may appear in comparison with others, is removed 

 to an immense distance, and that the surface of the earth 

 must have undergone material changes, from causes opera- 

 ting quietly through a long space of time, before these 

 extensive strata could have been shaped into distinct 

 mountains by the abrasions of their edges or the loss 

 of extensive portions ; before the separation of Staffa from 

 Mull, for example, could have taken place. The true 

 solution of these cases may perhaps never be discovered ; 

 but assuredly no theory of the earth can be just which 

 is incapable of being reconciled with the phenomena dis- 

 played by the latest rocks of the trap family. 



The last rocks to be described are those which occupy 

 the mountain district. 



In examining this tract I must regret that I can neither 

 define its geography more accurately, nor its geological 

 features with greater precision. The climate of this most 

 rainy island is not less inimical to accuracy of research 

 than its trackless and uninhabited mountains. But a 

 little defect of accuracy in asssigning the boundaries of 

 cognate rocks, will not probably be considered of any 

 moment in a survey of this nature. 



I need scarcely remind the reader that all the trap already 

 described, is characterized by a peculiarity in the external 

 outline, entirely different from that of the rock which 

 constitutes the mountain tract. I have already pointed 

 out the same circumstances in Sky, to which Mull has 

 in this, as in many other respects, a strong resemblance. 

 To what extent these forms may be connected with 

 geological circumstances in the origin of each district, 

 I am unable to conjecture. As far as I have examined, 

 it is impossible to trace such a connexion between these 

 mountain rocks and those stratified traps with the relative 

 antiquity of which we are tolerably acquainted, as to be 

 enabled to determine their comparative situations ; or 

 whether indeed there is any difference between them in 

 point of time. It is not improbable that there is such 



